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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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New Progress and Development Proposals of Sinopec’s PetroleumEngineering Technologies
LU Baoping
 doi: 10.11911/syztjs.2021001
[Abstract](35) [FullText HTML](12) [PDF 802KB](17)
Abstract:
During the 13th Five-Year Plan period, Sinopec has been continuously stepping up its scientific and technological efforts in view of the key technical problems in the efficient exploration and development of deep and ultra-deep oil and gas, tight low permeability oil and gas, and unconventional oil and gas. A number of technical bottlenecks restricting oil and gas exploration and development have been broken through; a batch of high-end technical equipment, downhole tools, instruments and fluids have been developed; a series of technologies have been formed including optimal fast drilling and completion, measurement and control under high temperature condition with high precision, fine logging and efficient reservoir stimulation. All promoted the efficient exploration and beneficial development of Shunbei ultra-deep oil and gas field and Fuling shale gas field, providing a strong technical support for increasing storage and stabilizing production in old oil fields and tight low permeability oil and gas fields. However, gaps still remain between the petroleum engineering technologies of Sinopec and foreign advanced technologies in the aspects of operation efficiency, technical index and comprehensive cost, etc. Thus, to provide Sinopec technical supports for stabilizing oil production, improving gas production and reducing cost, we must vigorously implement the innovation-driven strategy; largely enhance the ability of independent innovation; make breakthroughs in drilling and completion, logging and reservoir reconstruction and other professional key core technologies; and improve the level of petroleum engineering technology and equipment as soon as possible during the 14th Five-Year Plan period.
Key Technologies for Drilling and Completing Ultra-deep Wells in the Bozi 1 Block of Kelasu Structure
YIN Zhaohai, LI Guoqiang, WANG Hai, DING Yongliang, WANG Yun, LIU Changzhu
 doi: 10.11911/syztjs.2020130
[Abstract](53) [FullText HTML](9) [PDF 699KB](23)
Abstract:
Technical difficulties such as low ROP, long drilling cycle, poor cementing quality, and high drilling safety risk occur when drilling the upper part of complex ultra-deep wells in the Bozi 1 Block of the Kelasu structure. To break down these problems, a casing program was optimized in terms of regional geological characteristics and theoretical analysis; a series of technologies in ROP enhencment were optimized; combined evaporite bed determine technology was proposed, and a series of antileaking and lost circulation control technical measures and cementing measures were formulated. Consequently, key technologies for drilling and completion of complex ultra-deep wells in Bozi 1 Block of Kelasu structure were formed. The technologies had been tested in four wells including B1103 with an excellent potential for universal applicability. Compared with the neighboring wells using other drilling and completion technologies, there were many positive advances. For example, the ROP was increased by 34.4%, drilling cycle was reduced by 131 days, and completion cycle was cut by 141 days. This showed that the technologies could solve the technical difficulties in drilling and completion of ultra-deep wells reservoirs in the Bozi 1 Block, ensuring safe and efficient drilling and completion. Hence, the key technologies could be widely adopted in this block.
Applicability Evaluation of a Nano-Silica Modified Polymer in Reservoirs and Research on Micro-Oil Flooding Effect
LEI Tianmeng, WANG Xiujun, WANG Shanshan, CAO Jie
 doi: 10.11911/syztjs.2021016
[Abstract](34) [FullText HTML](7) [PDF 1192KB](4)
Abstract:
The solution characteristics and oil displacement effect of a nano-silica modified polymer with nanoparticle-polymer composites were evaluated to enhance the applicability of oil displacement polymers to reservoirs and further improve oil recovery. The performance differences between different polymer solutions, including a nano-silica modified polymer and two unmodified polymers, which were evaluated by Brookfield viscometer and HTHP Anton Paar rheometer at 90 °C and 20,000 mg/L of salinity. The oil-displacement properties are analyzed by core flooding experiments. As the next stage, the distribution of crude oil in the pore model before and after flooding with three kinds of polymers was observed through micro-oil flooding experiments. The experiment results showed that the interaction between the molecules of nano-silica modified polymer was stronger, and the molecular network had better performance in deformation recovery. Compared with the other two polymers, the nano-silica modified polymer can present much improvement in increasing viscosity, improving temperature resistance, salt resistance, enhancing shearing endurance and aging stability, and increasing the oil recovery ratio by 21%, which is greater than that of branched polymer (13%) and that of linear polymer (9%) respectively. So, the nano-silica modified polymer can effectively improve the heterogeneity of porous media, which greatly reduce the number of island-like oil beads and long strips of remaining oil in the porous media, and they significantly decrease the saturation of residual oil.
Borehole Strengthening Technology with Oil-Based Drilling Fluid in the Western Sichuan Basin
WANG Xingyuan, LU Dengyun, YUAN Zhiping
 doi: 10.11911/syztjs.2020116
[Abstract](164) [FullText HTML](51) [PDF 1199KB](29)
Abstract:
Wellbore collapse, lost circulation and sticking frequently happen in deep formations when drilling in the western Sichuan Basin. When drilling with oil-based drilling fluids, it is difficult for a thick filter cake to form. Plus, the low density of the filter cake leads to high pressure penetration ability at the wellbore. To solve this problem, based on the mechanism of drilling fluid film forming, a wellbore protection agent with the compact film, CQ-NFF, was synthesized from styrene, acrylate and other raw materials using the core-shell structural design, which is suitable for the middle layer with a temperature no more than 150 °C in deep well drilling in the area. According to the analysis results of the geological characteristics and engineering characteristics of high-risk formations and the d90 rule, an inner-filling plugging agent was formed from ultra-fine grains of calcium carbonate, elastic graphite, high strength resin and highly dispersed fiber. The film-forming mechanism and morphology of drilling fluid were analyzed by scanning electron microscope (SEM). Film forming effects were evaluated in filtration tests under high temperature and high pressure along with water and oil loss tests during drilling penetration at high temperature. By means of the sand bed filtration experiments under high temperature and high pressure, the plugging capacity of the filling material was evaluated. Experimental results show that CQ-NFF can form a compact film in water-in-oil emulsion and oil-based drilling fluid, and the film can be adsorbed on the surface of the filter cake effectively. The pressure resisting and plugging capacity of the film can reach 2.0 MPa. After the inner-filling plugging agent was added to the oil-based drilling fluid, the pressure bearing capacity of the inner filter cake was increased to over 3.5 MPa. The borehole strengthening technology with oil-based drilling fluid, treating chemicals as the core, was applied in Well Shuangtan 6 and Well Zhongjiang 2. The results show a remarkable application effect that the downhole downtime due to lost circulation in deep formations, wellbore collapse or drill pipe sticking were greatly reduced.
Failure Analysis and Improvements of Completion Packer in the High Temperature and High Pressure Gas Well of Kuqa Foreland
WANG Kelin, LIU Hongtao, HE Wen, HE Xinxing, GAO Wenxiang, SHAN Feng
 doi: 10.11911/syztjs.2020128
[Abstract](19) [FullText HTML](9) [PDF 1028KB](11)
Abstract:
Y443-111 packer is mainly used in the HPHT gas well in Kuqa Foreland, and pump suffocation is presented in five Wells during the process of fluid displacement. The packer in a part of Wells is setting ahead of time, resulting in the failure of the test mud to completely replace the packer fluid between the production casing and tubing, which seriously affects the integrity of the pipe string. In order to ensure operation safety in the high temperature and high pressure well, in view of the high temperature and high pressure when complex deep well completion packer for liquid in the process of failure and damage caused by packer downhole operation risk and safety accident problem, analyzes the packer for liquid in the process of failure and the cause of the damage and found the main factors influencing the packer invalidation is the packer and the casing clearance is small, the secondary reason for wellbore cleaning and displacement fluid flow rate. For this reason, the measures of reducing displacement fluid flow rate, conducting high-temperature aging test of mud, and reducing outer diameter of packer were formulated. The failure problem of packer was effectively controlled, and the success rate reached 97.6% after a total of 43 wells.
Research on Surface Tilt Mapping for “Hot Dry Rock” Stimulation in Gonghe Basin, Qinghai
ZHOU Jian, ZENG Yijin, CHEN Zuo, ZHANG Baoping, XU Shengqiang
 doi: 10.11911/syztjs.2020139
[Abstract](19) [FullText HTML](5) [PDF 1082KB](0)
Abstract:
Gonghe Basin in Qinghai Province is one of the favorite pilot test fields for Hot Dry Rock (HDR) resources in China. The three stages of hydraulic fracturing treatment in Well X1 were monitored from surface tilt mapping to better understand the fracture azimuth and length in the Gonghe Basin with enhanced geothermal systems (EGS), which would provide reference data in later deployment of adjacent wells and fracturing design. The fracture length and azimuth of Well X1 in the three stages of fracturing were obtained, and the mapping results were combined with geological features to analyze the impact of natural fractures on hydraulic fractures complexity in the target layers. The results demonstrated that some natural fractures are activated in the treatment and horizontal components of fractures are approximate to 50%, which will largely increase the complexity and heat transfer area of the fracture system. This research can provide a reference for fracturing optimization and the deployment of adjacent wells for geothermal development in Gonghe Basin of Qinghai Province.
The Applying of Direct Push Type Logging Technology in Northwest Oilfield
ZHANG Yu
 doi: 10.11911/syztjs.2021018
[Abstract](24) [FullText HTML](8) [PDF 1328KB](3)
Abstract:
There are many abnormal situations such as leakage and overflow in the carbonate reservoir in Northwest Oilfield, so conventional wireline logging cannot be carried out for construction safety. Due to the deep well and high hydrogen sulfide content, the drilling tools and casing annulus in some inclined or horizontal Wells are too small to carry out wireline drilling and transportation logging. For acquiring full logging data in complex environment, a new direct-push logging technology is proposed, which has no cable and no docking. The practical application in Shunbei, Tahe and some peripheral blocks shows that the direct-push logging has higher safety and reliability, shortens the time occupied by wellhead, greatly improves completion efficiency, and meets the requirement of "four increases (speed, efficiency, quality and production) and one reduction" in the current oil industry. It can ensure the safety of downhole instruments and wellhead in the Wells with complex well conditions or with well control risks, and can acquire all conventional data, which has far more advantages over traditional logging technology, and has very good practical significance for solving the problem of complex well logging in the Northwest oilfield. Up to now, direct-push logging has been applied to 25 Wells in Northwest Oilfield, and the acquisition rate of target logging data in Shunbei area has been increased from 31.25% to 90.91%. Through comparison and analysis, the logging data acquired by direct-push logging is true and reliable, which can meet the needs of reservoir evaluation and is worthy of popularization and application.
Laboratory-Scale Experimetal Study on Injection-Production Performance of A Multilateral-Well Geothermal System
SONG Xianzhi, LI Jiacheng, SHI Yu, XU Fuqiang, ZENG Yijin
 doi: 10.11911/syztjs.2021019
[Abstract](28) [FullText HTML](5) [PDF 1243KB](6)
Abstract:
Multilateral-well geothermal system is a novel geothermal development method using lateral wells to improve injectivity and productivity. In order to study the injection-production performance and its influence factors of the multilateral-well geothermal system, fluid flow and heat transfer experiments were conducted. Based on the multilateral-well geothermal experimental system and artificial rock samples, several experiments were conducted to evaluate the injection-production performance and to investigate effects of different factors on injectivity and productivity of the multilateral-well geothermal system. Also, the injection-production performances of the multilateral-well and single vertical well geothermal systems were compared. It indicates that decreasing injection temperature can reduce injection pressure and improve injectivity. Increasing lateral-well quantity and length can decrease the injection pressure and improve outlet flow rate. The injection-production performance of the multialtera-well geothermal system is obviously better than that of the single vertical well geothermal system. The findings prove that lateral wells can enhance the injectivity and productivity of the geothermal system, which provides the theoretical foundation for the field application of the multilateral-well geothermal system.
Key Technologies of Directional Drilling in Moxi-Gaoshiti, Sichuan Basin
LI Yongzheng, CHEN Tao, JIANG Chuan, DU Jiang
 doi: 10.11911/syztjs.2020103
[Abstract](29) [FullText HTML](6) [PDF 621KB](9)
Abstract:
When use bend stud in normal directional drilling for φ215.9 mm well bore in Moxi - Gaoshiti area of Sichuan basin Anyue gas field, could face quite difficulties, such as deep kick off points, high wellbore temperature, high drilling fluid density, complex formation, tough path control, hard and frequent backing pressure, etc. This article hereby has given out some analysis for the reason why its hard for directional drilling. And by bringing some key technologies of directional drilling like optimizing well bore path design, reducing friction and resistance, optimizing drill bit and stud, hydro-oscillator, auxiliary speed up kit w/ sway drilling tools, etc, to practice in location, it have seen a positive reduce on the backing pressure, and a rising rate of penetrate, which potentially decreasing the pipe-sticking possibilities. φ215.9 mm section directional drilling term has been reduced from 44.75 days in 2017 to 27.51 days in 2019 which is a prominent raise for ROP. The result indicates that the key technologies brought out from this article gives a good impact for resolving the directional drilling difficulties of the φ215.9 mm high temperature, high density, deep well bore in Moxi-Gaoshiti area and recommend a further extension in this area.
Development status and suggestions of big data technology in petroleum engineering industry
GENG Lidong
 doi: 10.11911/syztjs.2020134
[Abstract](49) [FullText HTML](4) [PDF 952KB](42)
Abstract:
Big data has gradually become one of the most important methods for oil companies and oil service companies to realize the intelligence of petroleum engineering and cost reduction and efficiency increase. Big data has become a research hotspot at home and abroad. In order to promote the rapid development and widespread application of big data technology in the oil and gas industry and accelerate the transformation of digitalization and intelligence of petroleum engineering, this article introduces the definition and characteristics of big data. The current application status of big data in petroleum engineering is analyzed from two aspects: big data platforms and specific application scenarios. The development suggestions of big data technology in petroleum engineering are proposed. It is recommended that the unified big data platform should be established. The digital giants should be cooperated with together to investigate the technology. The data management and technical standard need to be modified. The basic and prospective researches should be strengthened. The related research projects should be implemented for specific application scenarios and then the big data ecosystem will be formed gradually. The big data technology has a broad application prospect in the petroleum engineering industry. It is of great significance for promoting the economic and efficient development of oil and gas to accelerate the investigation and application of big data in petroleum engineering.
Current Situation and Development Suggestions of Water-soluble Gas Development Technology at Home and Abroad
HE Yongming, XIE Wangyang, CHEN Xianchao
 doi: 10.11911/syztjs.2020121
[Abstract](27) [FullText HTML](10) [PDF 757KB](10)
Abstract:
Water-soluble natural gas (referred to as water-soluble gas) is a new energy with huge reserves. It has great development potential and prospect. At present, there is a lack of systematic theoretical research and mature development technology. The distribution and development status of water-soluble gas reserves at home and abroad are introduced in detail. In this paper, the research progress of water-soluble gas development technology at home and abroad is summarized, including produced water reinjection technology, the basic principle and field test of geothermal water-soluble gas extraction and carbon dioxide geological storage technology, as well as the research progress of the influence of gas-water interface and water invasion law. According to the analysis, although some research achievements have been made in the research of water-soluble gas development technology, no systematic theoretical system has been formed, and no comprehensive utilization, economical, effective, safe and reliable development technology has been developed. Therefore, it is necessary to attach great importance to the research on the exploration and development technology of water-soluble gas, so as to realize the effective exploration and development of water-soluble gas in China and provide new ideas for ensuring national energy security.
Drilling & Completion Technology of CBM Horizontal Well in Yellow River of Baode Coalbed Methane Field
DENG Junyao, LIU Yishan, QIAO Lei, WANG Kailong, HU Kai
 doi: 10.11911/syztjs.2020124
[Abstract](36) [FullText HTML](10) [PDF 782KB](10)
Abstract:
In order to realize the effective use of high-quality CBM reservoir in the northern part of Baode Coalbed Methane Field, which is affected by complicated ground conditions such as urban and Yellow River overburden area, the optimization technology of drilling and completion of long CBM horizontal wells has been formed. Through the in-depth analysis and evaluation of the geological characteristics of the coal seam in the region, under the conditions of coal seam dip angle, vertical depth and conventional drilling technology, the optimization design method for drilling and completion of intensive horizontal wells has been formed through well structure optimization, well trajectory measurement and control, optimization of drilling fluid system and completion technology. Pilot test had also been carried out. Through the integrated application of new technology, the economic exploitation of high-quality CBM reserves in surface complex areas can be realized. The limit footage design can reach 1 700–2 000 m under the condition of 800–1000 m vertical depth and 2–5° upward inclination angle of coal seam. The developed FRP screen completion system realizes the re-entry of the completion wellbore. The function of fracturing and washable wells, and meeting the integration policy of coal mining and gas production. The field application of drilling and completion technology in long horizontal section of CBM provides a new technology and method for the development of CBM in Yellow River overburden area of Baode Coalbed Methane Field.
Characteristics of Acoustic Field Ahead of Drill-bit in Acoustic Logging While Drilling
YANG Shubo, QIAO Wenxiao, ZHAO Qiqi, NI Weining, WU Jinping
 doi: 10.11911/syztjs.2021020
[Abstract](24) [FullText HTML](7) [PDF 2205KB](4)
Abstract:
As the existing acoustic logging tools cannot meet the requirements of look-ahead detection, the exploratory research of look-ahead acoustic logging-while-drilling (LWD) is developed based on the phased array technology. The directional-radiation and scanning-reception of acoustic energy are realized by using the phased array acoustic transmitters and receiver stations. The responses of monopole and phased array acoustic LWD tools in a situation involving a formation interface ahead of the drill bit are numerically simulated using the finite difference algorithm. The results show that, the acoustic fields of look-ahead acoustic LWD are more complex than those of conventional reflection acoustic logging, because of the wave scattering at the well bottom. Compared with the monopole acoustic transmitter, the amplitudes of echo P-P waves can be considerably increased by directionally enhancing the energy radiated to the formation ahead of the drill bit, based on the linear phased array acoustic transmitter. Compared with the monopole acoustic receiver, the azimuth angle of the formation interface ahead of the drill bit can be obtained approximatively by analyzing the amplitude distribution of echo P-P waves in the scanning-reception waveforms, based on the arcuate phased array acoustic receiver station. The study confirms the feasibility of detecting geological anomalies ahead of the drill bit using phased array acoustic logging, and provides the theoretical basis for the development of industrial prototypes.
Key Technologies of Karstic Geothermal Reservoirs Drilling in Beijing-Tianjin-Hebei Region
CAO Huaqing, WU Bo, LONG Zhiping, WANG Dianxue, HUANG Ganting, MA Xiangdong
 doi: 10.11911/syztjs.2020105
[Abstract](103) [FullText HTML](12) [PDF 959KB](25)
Abstract:
The drilling technology of Karst geothermal storage in Beijing-Tianjin-Hebei region mainly depends on the transplantation and application of key technologies such as oil and gas drilling technology and petroleum geology. In order to effectively solve the problems such as serious lost circulation of drilling in the stratum of weathering crust of karstic geothermal reservoirs, borehole wall collapse and buried drilling tools, difficulty in bit selection and low drilling rate of limestone stratum. On the basis of fine depiction of regional geological features and detailed analysis of formation lithological characteristics, the rate of penetration is improved by optimizing well structure, optimizing drilling mode and optimizing personalized drill bit. By using XRF logging technology to accurately judge weathering crust in advance and accurately, the buried drilling tools after the loss of drilling fluid is eliminated and the well completion rate is improved. With the comprehensive application of the above technologies, the completion rate of karstic geothermal reservoirs drilling in beijing-tianjin-hebei region is 100%, the footage of single drill bit is increased, rate of penetration is stable, and the drilling cycle is shortened. It plays a guiding role in the subsequent exploration, exploitation and utilization of geothermal resources in the beijing-tianjin-hebei region.
Study on Preparation and Properties of Multy-porosity Shape Memory Polyner for Well Completion
DUAN Youzhi, HOU Qian, LIU Jinchun, YUE Hui, AI Shuang, XIN Weidong
 doi: 10.11911/syztjs.2020100
[Abstract](32) [FullText HTML](2) [PDF 987KB](1)
Abstract:
The performance of porous shape memory polymer prepared from polyols in single relative molecular weight behave badly for well completion, so it is necessary to prepare the porous shape memory polymer with polyols in different relative molecular weight (thermo-sensitive RPUF in this paper). Different porous shape memory polymers are prepared by changing the molecular weight ratios of polyols to guide the preparation of porous shape memory polymer suitable for different downhole conditions. Then the influence of molecular weight ratios of polyols on their properties is analyzed by testing mechanical properties, glass transition temperature, and thermal sensitivity and observing pore structure. Smaller weight ratios of polyols in low relative molecular weight to those in high relative molecular weight can bring higher hardness, compressive strength, bending strength, and glass transition temperature of porous shape memory polymers, lower temperature for thermal deformation and the later recovery, smaller open areas, larger sizes, pattern coefficients, and wall thicknesses of pores, and stronger structural anisotropy. The results reveal that a porous shape memory polymer for well completion can be obtained by adjusting the molecular weight ratios of polyols in the raw materials. With certain mechanical strength, it can recover the shape at different downhole temperatures and filter sand with different formation median grain sizes.
Experimental Study on Rock Breaking Efficiency with Ultrasonic High Frequency Rotary-Percussive Drilling Technology
LU Zongyu, ZHENG Junsheng, JIANG Zhenxin, ZHAO Fei
 doi: 10.11911/syztjs.2020126
[Abstract](28) [FullText HTML](3) [PDF 867KB](14)
Abstract:
In order to investigate the speed-up effect of ultrasonic high frequency rotary–percussive drilling technology compared with conventional rotary drilling technology, and the influence of different drilling conditions and parameters on high frequency rotary–percussive rock breaking, the ultrasonic vibrator was designed, and the ultrasonic rock breaking simulation test bench was built. By the controlled variable method and the orthogonal experiment method, carried out the ultrasonic rock breaking speed-up test and the ultrasonic rock breaking influence factor analysis test, and studied the influence law of the weight on bit, the ultrasonic amplitude, the speed and the bit diameter on the ultrasonic high frequency rotary–percussive breaking rock. The test results show that, compared with conventional rotary rock breaking technology, the ultrasonic high frequency rotary drilling technology has a higher efficiency of rock breaking under conventional temperature and pressure conditions in the laboratory, with an average speed increase of 77.7%. The impact on the ultrasonic high frequency rotary–percussive rock breaking efficiency ranges from large to The lower order is: weight-on-bit, amplitude, drill bit diameter, speed; weight-on-bit and amplitude have a highly significant effect on the efficiency of ultrasonic high frequency rotary–percussive rock breaking, and the larger the amplitude, the higher the efficiency of ultrasonic high-frequency rotary rock breaking. The study of the rock breaking effect of ultrasonic high frequency rotary–percussive drilling technology provides a new rock breaking method for increasing the drilling speed of deep hard formations.
Study on Sand Control Technique of Gravel Packing Combined with Water Control for Horizontal Wells
ZHOU Hongyu, WAN Xiaojin, WU Shaowei, ZHANG Bin, KONG Yang
 doi: 10.11911/syztjs.2020138
[Abstract](72) [FullText HTML](10) [PDF 2111KB](11)
Abstract:
To meet the dual demands of water control and sand control, and to solve the difficulties in gravel packing by using water control screen and subsequent formation treatment, a novel AICD screen with by-pass sliding sleeve was designed and matching technologies were improved, based on which a sand control technique of gravel packing combined with water control for horizontal wells was proposed. The sliding sleeve can provide additional flow channel to decrease treating pressure and can be opened or closed on the demand to complete formation treatments and enhance liquid production. A gravel packing simulation test platform for horizontal well was designed to verify its feasibility, it can record pressure and flow rate data at real-time, to quantitatively analyze and visually evaluate water control packing process. Comparative simulation tests of conventional AICD screen and novel AICD screen with by-pass sliding sleeve were carried out. The test results showed that gravel packing efficiency of AICD screen with by-pass sliding sleeve can reach 100% with a flow rate of 0.40 m3/min and a sand concentration of 4%. Compared with conventional AICD screen, the novel screen had characteristics of lower displacing pressure, shorter working time, and more compact sand. Besides, the sliding sleeve showed good switching performance. The result show that the structure of the AICD screen with by-pass sliding sleeve is reasonable and the matching packing water control technique is feasible, it can provide a new solution for sand control completion combined with water control for horizontal well.
Research on Dynamic Geological Model Geosteering based on Kalman Filter
LU Ziqing
 doi: 10.11911/syztjs.2020135
[Abstract](37) [FullText HTML](12) [PDF 1884KB](9)
Abstract:
The lateral variation of the reservoir under complex geological conditions will seriously affect the drilling rate of horizontal Wells. The drilling trajectory needs continuous dynamic optimization to ensure that the well is in the best geological target. Based on the regional geological logging data, the initial geological model including the current structure and attribute knowledge is established. The measurement while drilling(MWD) and logging while drilling(LWD) data are processed by Ensemble Kalman Filtering(EnKF) method to calculate the formation thickness and dip angle of the target area to form a more accurate and timely geological understanding; then, the up-to-date geological information is input into the initial model to update the structure and geological attribute. The bit target would be optimized in time under the control of the up-to-date geological model. YP1 well geosteering examples show that the use of the dynamic geological model geo-steering process, the key target according to thickness, dip Angle and attribute analysis, the dynamic geological model provides adjustment strategies at key targets, finally we achieve the rate of 92.1% during the 1901 meters drilling in horizontal well section.
Prevention and plugging technique of deep coal bed methane well in Yanchuannan Block
PENG Xing, ZHOU Yucang, ZHU Zhichao, WANG Junfeng
 doi: 10.11911/syztjs.2020133
[Abstract](39) [FullText HTML](10) [PDF 958KB](4)
Abstract:
The deep coalbed methane resources in Yanbei block is rich, but lost circulation during the drilling of gas wells has become serious. Lost circulation has become a major obstacle hindering the development of the coalbed methane. In order to reduce the frequency of lost circulation, minimize the economic cost induced by lost circulation, and ensure the safe and efficient well construction, It is very important to form a leakage prevention and closure strategy. In this paper, the geological characteristics of the research area were summarized. Research shows that the pores in the middle and upper formations are developed, the plugging capacity of the drilling fluid is insufficient. Therefore, the type of lost circulation in the middle and upper formation is pore lost circulation. The natural fractures in the reservoir section are developed, as well as the plugging capacity of the drilling fluid is insufficient. The formations are dominated by fractures and fracture propagation losses. Based on this, the anti-leakage technical scheme are proposed for the vertical well section: the formula of original drilling fluid+5% plugging material drilling fluid is appropriate for the upper pore type lost formation, the formula of original drilling fluid+7% plugging material drilling fluid is appropriate for the lower fracture type lost formation, the formula of original drilling fluid + 10% plugging material drilling fluid formula is appropriate for the fractured reservoirs section. Pressure-bearing plugging technique is used in the inclined well section, and therefore a portable pressure-bearing plugging tool was developed. The comprehensive anti-leakage and plugging technology has a good field application effect, and the frequency of lost circulation and the processing time of lost circulation have been greatly reduced.
Optimized Drilling and Completion Technology for Horizontal Wells of Unconventional Reservoirs in Jilin Oilfield
CUI Yueming, SHI Haimin, ZHANG Qing
 doi: 10.11911/syztjs.2020123
[Abstract](65) [FullText HTML](14) [PDF 693KB](13)
Abstract:
In view of the problems of high cost, long drilling cycle, slow ROP, unstable borehole wall, high friction and torque, and difficult casing running in Unconventional Reservoir of Jilin Oilfield, this paper studies the optimized drilling and completion technology of horizontal well in two-stage casing program with shallow surface casing. In order to reduce the cost from the engineering design, the three-stage casing program in the early stage was simplified to a two-stage one with shallow surface casing, and the time of one opening was saved. At the same time, the technical measures such as profile design of double exploration and double stabilization, low-filtration strength suppression polymer drilling fluid system, near-bit geological guiding tool, customizing the PDC bit design, floating casing and cementing and so on were adopted.The technical measures were applied in 180 wells in the field of unconventional tight oil horizontal wells in Jilin Oilfield, with an average well depth of 3449 m, an average horizontal length of 1189 m, casing safety entry rate of 100%, cementing qualified rate of 100%, increasing in reservoir drilling rate of 20.2%, shortening drilling cycle of 44.2% and reducing investment costs of 40.7%. The research results achieve the goal of low cost and high efficiency development of unconventional tight oil horizontal wells in Jilin Oilfield, and can provide a reference for the development of unconventional gas reservoirs such as tight gas and shale oil in Jilin Oilfield.
Key Technologies for Slim Hole Drilling in the Southern Sulige Block
YANG Jing, TU Fuhong, HUO Rujun, TAO Ruidong, SHANG Zibo, GUO Liang
 doi: 10.11911/syztjs.2020082
[Abstract](199) [FullText HTML](32) [PDF 692KB](48)
Abstract:
Technical difficulties have been encountered in slim hole drilling in the Southern Sulige Block. The difficulties include bit selection, well trajectory control, frequent sticking during electrical logging, severe lost circulation and low penetration rate, etc. Therefore, researches on key technologies such as PDC bit optimization, PDM tool improvement, BHA optimization, well trajectory control, optimal selection of drilling fluids systems, anti-leakage and plugging were carried out, and formed key technologies for slim hole drilling in the Southern Sulige Block, which were applied in more than 80 wells. Field applications suggest that the improved PDC bit has stable performance, with high penetration rate. Among them, the drilling cycle of 6 wells is less than 10 days; the optimized BHA and PDM tools can meet the requirement of “two-run drilling” in the second-spud section. By implementing the strategy of controlling the drilling fluid density, reducing the pressure loss and pre-adding plugging material while drilling the thief zone, etc., remarkable anti-leakage and plugging effects were achieved; Drilling fluid properties have been optimized to improve the success rate of one-time electrical logging. The key drilling technologies for slim holes in the Southern Sulige Block have provided technical support for safe and efficient slim hole drilling on this area.ea.
The Technical Advance and Development Suggestions for Leakage Prevention and Plugging Technologies in the Tarim Oilfield
WANG Tao, LIU Fengbao, LUO Wei, YAN Zhihang, LU Haiying, GUO Bin
 doi: 10.11911/syztjs.2020080
[Abstract](101) [FullText HTML](39) [PDF 606KB](35)
Abstract:
With the goal of solving the problem of circulation lost under complicated geological conditions of the Tarim Oilfield, this paper analyzed the types of circulation lost in this oilfield combining its formation characteristics, and summarized the development history and achievements of leakage prevention and plugging technologies in this field. It shows that leakages induced by porosity, fracture and caverns are all encountered in Tarim Oilfield, but mainly caused by fractures and cavity. The development of leakage prevention and plugging technologies in this oilfield has undergone two stages: the establishment of basic system and the development and perfection of characteristic technology. A series of techniques have been formed such as oil-based drilling fluid leakage prevention and plugging, high-strength pressure-bearing plugging, high-pressure brine layer leakage prevention and plugging, and fracture-cavity leakage plugging. From the analysis and sorting, we have clarified the current status of leakage prevention and plugging techniques in Tarim Oilfield and the remaining challenges in leakage control, and determined the trend of research. We proposed suggestions for further development of those technologies, such as strengthening formation prediction, developing or introducing new plugging technologies, enriching engineering techniques, and developing big data plugging software.
Cementing Technology Applied in the Parahuacu Oilfield of Ecuador
LI Wandong
 doi: 10.11911/syztjs.2020109
[Abstract](91) [FullText HTML](29) [PDF 978KB](7)
Abstract:
When cementing a well in the Parahuacu oilfield of Ecuador, edge-bottom-water channeling is very likely to occur in the second interface in which cement slurry filtrate and solid particles easily intrude into the reservoir pore throat, and cement slurry with conventional density may leak into the reservoir. To solve those problems, an acidic flush fluid, a temporary plugging spacer and an interfacial cementing enhancer were developed through simulated flushing tests. Keeping those factors in mind, a multi-effect cementing pad fluid was prepared with them. A low-density cement slurry containing anti-channeling latex was developed with a micro hollow glass ball while considering the liquid-solid ratio, fluid loss control and anti-channeling performance. Indoor testing results show that by using the multi-effect cementing pad fluid, 95.0% structural mud cake on the sidewall was removed, the permeability recovery of the reservoir reached over 90.0%, the interfacial cementing strength increased more than 5 times. The cement slurry with anti-channeling latex has a density of 1.74 kg/L, its performance is stable, API fluid loss does not exceed 20 mL and static gel strength transition time is less than 10 min. The newly developed cementing technology, including the above-mentioned pad fluid, cement slurry and relevant supporting technical measures (such as centralizer placement, displacement scheme design), was then applied to 5 wells in Parahuacu oilfield. In the field application, casing centralization was up to 85.8%, annulus displacement efficiency of cement slurry exceeded 95.0%, no leakage of cement slurry or edge-bottom-water channeling was found in the reservoir. The new cementing technology in the Parahuacu oilfield has achieved significant effect and can solve existing problems in reservoir cementing.
Lost Circulation Control Performance Evaluation and Application of Elastic Mesh Materials
LI Gongrang, YU Lei, LIU Zhendong, LI Hui, MING Yuguang
 doi: 10.11911/syztjs.2021008
[Abstract](10) [FullText HTML](2) [PDF 928KB](1)
Abstract:
In order to solve the problems of existing conventional bridge slurry plugging materials, such as weak crack adaptability, shallow plugging layer and low plugging success rate. For this reason, this article has selected an elastic mesh material, and used compression resilience, tensile strength, temperature resistance and other performance evaluation experiments to investigate the influence of the size, shape and concentration of the elastic mesh material on the plugging effect. Experimental results indicated that the 50% compression set rate of 1# elastic mesh material was less than 10%, the tensile strength was 150 kPa, and the temperature resistance was 150 ℃, which was suitable for use as a plugging material. The cubic elastic mesh material could stay in the cracks effectively with excellent plugging effect. The elastic mesh material with the size of 5 mm×5 mm×5 mm had the best sealing effect for the wedge-shaped joint with the seam width of 5×4 mm. The best concentration of the elastic mesh material was 0.08%. The elastic porous mesh plugging material has been applied on-site in multiple wells, and the success rate of one-time plugging has reached 86.7%. Research has shown that the elastic porous mesh plugging material had good adaptability and plugging effect to the fractured leakage layer, and could solve the leakage problem of the fractured formation.
Self-Healing Cementing Technology in Carbonate Formation of Manshen 1 Well
WU Bozhi, ZHANG Huaibing
 doi: 10.11911/syztjs.2020071
[Abstract](66) [FullText HTML](9) [PDF 827KB](10)
Abstract:
Manshen1 is a key exploration well deployed in the new exploration area on the South Bank of Tarim Oilfield, with a buried depth of nearly 8000 m. It is difficult to ream due to serious block drop during drilling in carbonate fractured formation of the third spud; Silurian and Yijianfang formations are prone to lost circulation. There are some technical problems in cementing, such as irregular well diameter, low displacement efficiency, insufficient cement return caused by lost circulation and wellbore integrity. In order toensure smooth cementing and good cementing quality, through the optimization of high-temperature plugging fluid, design contact time > 20 min, improve the displacement efficiency, optimize the self-healing water slurry system, cement stone can automatically repair micro fractures when encountering oil and gas, and has secondary self-healing recovery ability, so as to ensure the wellbore integrity in the whole life cycle. By fully analyzing the geological data, correctly judging the location of lost circulation layer and adopting the forward injection and reverse extrusion cementing technology, the cementing operation is smooth. It ensures the effective cement sealing of Lower Ordovician, Silurian and casing overlap section, and excellent cementing quality evaluation in later stage, which provides certain technical reference for cementing construction in this area.
Experimental Study of Decreasing Deep Well Drilling Fluid Temperature Based on Phase Change Heat Storage Principle
LIU Junyi, CHEN Erding, LI Guangquan, YUAN Li
 doi: 10.11911/syztjs.2020131
[Abstract](56) [FullText HTML](7) [PDF 814KB](19)
Abstract:
The high temperature stability of drilling fluids and down-hole instruments still could not meet the requirements of deep or ultra-deep wells drilling engineering. In order to solve these technical problems, phase change materials were firstly introduced into drilling fluids to conduct experimental study of decreasing deep well drilling fluid circulating temperature based on the phase change heat storage principle. The heat storage characteristics of phase change materials were investigated based on the thermo-physical property tests of phase change materials. The influence of phase change materials on the rheological and filtration properties of drilling fluids were comparatively evaluated, and the drilling fluid circulation temperature cooling curves were also measured using homemade drilling fluid circulation simulation experiment device. Laboratory experimental results showed that the phase change temperature of the phase change materials 1#~3# was about 120~145 ℃ and the latent heat of phase change was about 90.3~280.6 J/g, and the phase change materials 2# displayed best phase change heat storage characteristics with the highest latent heat of phase change. The phase change materials did not affect the stability of drilling fluids and the rheological and filtration properties still met the demand of drilling process even after increasing the concentration of the phase change materials to 12%. When the concentration increased to 12%, the drilling fluid circulation temperature could be reduced by about 20 ℃. Furthermore, the phase change materials exhibited good reuse performance, and it could continuously conduct the phase change process of heat storage and heat release, which met the drilling fluid circulation requirement. The feasibility of decreasing drilling fluid circulating temperature based on the phase change heat storage principle, was finally proved, which could provide a technical reference for the further study of deep well high temperature drilling fluid cooling technology.
Optimal and Fast Drilling Techniques of Shale Oil Horizontal Well in Cangdong Sag
LIU Tianen, ZHANG Haijun, YUAN Guangjie, LI Guotao, YIN Qiwu, CHEN Fei
 doi: 10.11911/syztjs.2020127
[Abstract](42) [FullText HTML](8) [PDF 1164KB](12)
Abstract:
During the drilling process of shale oil horizontal wells in Cangdong Sag, the drilling speed is slow, the safety risk is high, and the cementing quality is difficult to guarantee, which restricts the benefit exploration and development of shale oil. Through the fine prediction of formation leakage pressure and collapse pressure, the Optimization Research on well trajectory and well structure, and the matching technologies such as brine drilling fluid system, high-efficiency PDC bit, rotary steering drilling technology, ductile cement slurry system and floating displacement cementing are integrated and applied, forming the optimal and fast drilling technology for shale oil horizontal wells in Cangdong Sag. The technology has been applied in 20 shale oil horizontal wells in Cangdong Sag, and the cementing quality has been improved by 30.4%. The average ROP of wells with a depth of more than 4500.00 m has been increased by 20.2%, and the average drilling cycle has been shortened by 30.6%; the average ROP of wells within 4500.00 m has been increased by 82.9%, and the average drilling cycle has been shortened by 49.9%, which meets the requirements of optimal and fast drilling of shale oil horizontal wells. The research and application show that the optimized and fast drilling technology for shale oil horizontal wells in Cangdong Sag provides a means for the benefit exploration and development of shale oil horizontal wells, and also provides a reference for the drilling technology optimization of unconventional oil and gas reservoirs in domestic oilfields.
Leak-proof plugging technology for Mishrif carbonate reservoir in Halfaya Oilfield of Iraq
XIE Chunlai, HU Qingfu, ZHANG Fengchen, BAI Zhongwei, YIN Chuanming, SI Xiaodong
 doi: 10.11911/syztjs.2020125
[Abstract](41) [FullText HTML](9) [PDF 821KB](8)
Abstract:
In order to solve the problem of drilling fluid loss in the drilling operation of carbonate fractured cavernous reservoirs in Halfaya Oilfield, under the analysis of Halfaya Oilfield formation conditions, fractures type, leakage factors and degree of leakage are analyzed, The target area is divided into areas of leakage type, and the plugging materials and the plugging formula are optimized, forming the prevention and control technology of the leakage area, the partial leakage area and the comprehensive treatment technology for the malignant leakage area and the complete leakage area. In the past two years, this technology has been applied in 21 MISHRIF directional wells, According to statistics, compared with the average level of the previous three years, the loss of drilling fluid has been significantly reduced. The loss of each well has been reduced from 472 m3 to 29 m3, and the rate of complex time has been by 12.5%, the drilling cycle has been shortened by 8.5%, the application effect is significant. this technology has reference significance for solving the problem of drilling loss in carbonate fractured cavernous reservoirs in other blocks.
Hardening Properties and Enhancement Mechanism of Modified Alumina Cement at Negative Temperature
LIU Haoya, BAO Hongzhi, LIU Yaqing, HE Qingshui, HU Zhiqiang, JIN Xin
 doi: 10.11911/syztjs.2020129
[Abstract](21) [FullText HTML](8) [PDF 1373KB](7)
Abstract:
According to the hydration reaction of water and cement unable to proceed under negative temperature, difficult to meet the demand of cementing, carrying Out Research Study in Hardening Properties and Enhancement Mechanism of modified alumina cement.The change law of the setting time, fluidity and compressive strength of cement at different curing temperatures of 0, –10, –18 ℃ and the relationship between they and the main components was studied by contrast method. Based on the analysis of the phase components, gypsum was added to promote the formation of AFt and increase the compressive strength of the negative temperature cement. The results of experimental study show that this cement slurry have fine curing properties at negative temperature 0 ℃ to –18 ℃, setting time is 0.5–3.0 h when SCEG content is 0%–3%; compression strength in 24 hrs can reach 9.7–11.2 MPa and adding 10%–15% gypsum can be increased about 30%. XRD analysis showed that the mainly hydrated mineral of negative temperature cement is Aluminate clinker but not Silicate clinker; hydration products is Ca2Al(Al,Si)2O7、AFm、AFt and a few C–S–H. The higher the content of AFt, the higher the compressive strength of cement stone. The results show that modified alumina cement possesses good Hardening Properties and the addition of a proper amount of gypsum can increase the content of AFt in hydrated mineral of negative temperature cement and helpful to improve the compressive strength of cement stone.
Analysis and Optimization of Construction Parameters for Preventing Casing Deformation in the Changning Shale Gas Block, Sichuan Basin
CHEN Zhaowei, HUANG Rui, ZENG Bo, SONG Yi, ZHOU Xiaojin
 doi: 10.11911/syztjs.2020108
[Abstract](62) [FullText HTML](16) [PDF 1750KB](10)
Abstract:
In order to solve the problem of casing deformation in the Changning shale gas block in the Sichuan Basin, the construction parameters of wells with deformed casing were analyzed and optimized. The fracture and in-situ stress model of the platform H were established based on 3D seismic data, logging and test data. The hydraulic fracturing numerical simulation was conducted based on the Mohr-Coulomb critical stress and mass conservation law. Based on the classification of slip risk, the relationship between the construction parameters for fracturing and activation of fracture zones was analyzed. The statistics and analysis results showed that when only fluid volume reduction measures were taken, the casing deformation ratio in fractured zones was 21.7%. When only the flowrate reduction measures were taken, the casing deformation ratio was 8.1%. It can been seen from fracturing simulation that, for those faults with high slip risk, when the fluid volume is reduced by 20%, the length of activated fault and the number of activated fractures are decreased by 17% and 26%, respectively. When the flowrate is reduced by 20%, the length of activated fault and the number of activated fractures are reduced by 3% and 6%, respectively. For those faults with medium slip risk, when the fluid volume is reduced by 20%, the length of activated fault and the number of activated fractures are decreased by 22% and 30% respectively. When the flowrate is reduced by 20%, the length of activated fault and the number of activated fractures are decreased by 43% and 60%, respectively. The research results showed a suggestion on construction parameters that reducing fluid volume for high slip risk faults and reducing flowrate for medium slip risk faults. This could provide a reference for solving casing deformation problem on site.
Preparation and Performance Evaluations of an Ultra-low Permeability Film-Forming Agent based on Graphene Modification
WANG Weiji
 doi: 10.11911/syztjs.2020104
[Abstract](39) [FullText HTML](11) [PDF 1406KB](7)
Abstract:
In order to prevent the drilling fluid filtrate from entering the formation, to maintain the wellbore stability and to protect the reservoir, a procedure to activate a graphene surface was conducted by using a modified Hummers method. It introduced carboxyl, hydroxyl, epoxy groups and other active groups, resulting in a kind of graphene modified film-forming agent SMSL with ultra-low permeability. It was prepared by grafting copolymerization with selected monomers on the surface of active graphene. The molecular structure, micro morphology and dispersive state of SMSL were analyzed by the infrared spectrometer, the element analyzer, the atomic force microscope and the synchronous thermal analyzer. Researchers used pressure transfer tests, core self-seepage tests and SEM to evaluate the dense film-forming plugging characteristics of SMSL and the compatibility of SMSL with the water-based drilling fluid. The results showed that the molecular structure of SMSL met the design requirements, and it could significantly reduce the pressure transfer and self-seepage effect of rocks. Specifically, the shale film-forming efficiency was 162.96% higher than that of the conventional polymer film-forming agent, the self-seepage capacity of tight sandstone was decreased by 88.74%, with very good compatibility with the water-based drilling fluid. The research indicated that when SMSL was added into the drilling fluid, a dense film can form on the wellbore to prevent the filtrate from entering the formation and thus can maintain wellbore stability and protect the reservoir.
Difficulties and Technical Countermeasures for Automatic Vertical Drilling in Ultra-Deep Wells in the Bozi Block of the Tarim Basin
TENG Xueqing, LIU Hongtao, LI Ning, WANG Tianbo, RU Dajun, DONG Ren
 doi: 10.11911/syztjs.2020113
[Abstract](52) [FullText HTML](9) [PDF 649KB](20)
Abstract:
The Bozi Block of the Tarim Basin belongs to a typical piedmont high steep structure that has a large dip angle and strong natural deviation capacity, which is difficult for deviation-prevention straight drilling. It is hard to ensure the hole deviation control effect by using conventional deviation-prevention straight drilling technology. This paper analyzes difficulties in the application of automatic vertical drilling technology in ultra deep wells of the Bozi Block. In view of the strong downhole vibration and the difficulty in deviation prevention during straight drilling in the upper conglomerate formation of Bozi Block, research on deviation-prevention technology was carried out on a number of different aspects. They included damping optimization, ultra deep well signal transmission, the optimization of deviation-prevention straight drilling process, etc. The automatic vertical drilling system was applied in the spud in sections of 198–417 m and 565–1 000 m in Well BZ1501. The cumulative working time of two trips was 281 h, the average ROP was 2.43 m/h, and the hole deviation was 0.2°. Compared with the conventional pendulum drilling string used in this well and the automatic vertical drilling system in Well BZ18, the system had the advantages of long service life, high ROP and good deviation control effect. The field application demonstrated that the deviation-prevention straight drilling technology could be successfully implemented for ROP enhancement in the ultra deep wells of the Bozi Block in the Tarim Basin, and its application could be popularized in the block.
Cover
2020, 48(6): 0-0.  
[Abstract](66) [FullText HTML](25) [PDF 18015KB](40)
Abstract:
contents
contents
2020, 48(6): 1-1.  
[Abstract](1235) [FullText HTML](473) [PDF 348KB](57)
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2020, 48(6): 2-2.  
[Abstract](47) [PDF 453KB](11)
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Expert Viewpoint
Technical Status and Development Suggestions in Exploiting Geothermal Energy from Abandoned Wells
SONG Xianzhi, XU Fuqiang, SONG Guofeng
2020, 48(6): 1-7.   doi: 10.11911/syztjs.2020120
[Abstract](179) [FullText HTML](48) [PDF 866KB](43)
Abstract:
Geothermal energy, as one of the renewable energy resources replacing fossil fuels, is difficult to drill and utilize in a large-scale due to its high development cost. A large number of oil and gas wells are abandoned in the petroleum industry every year. If those wells can be used in geothermal energy development, it not only alleviates energy problems and reduces drilling costs, but also effectively controls pollutions from well abandonment. Therefore, the feasibility of the abandoned wells transformation was analyzed combining with the current research status of geothermal exploitation and the selection and utilization methods of target wells were elaborated. In addition, the transformation and heat extraction modes in abandoned wells were discussed in this paper. In general, the exploitation of geothermal energy from abandoned wells is still in the stage of theoretical and experimental research, far from large-scale industrial application. It is suggested to start from the overall trend of geothermal development, focus on key technologies of multi-lateral wells, improve the heat extraction performance of abandoned well systems, establish the intelligent decision-making and optimization system, and strengthen the research on ground supporting facilities. The results of the research and development suggestions will provide a guideline in obtaining geothermal resources from abandoned wells.
Drilling & Completion
Key Technologies for Drilling and Completing Shallow Slim Hole Sidetracking Horizontal Wells in the Jidong Oilfield
LI Yunfeng, PAN Junying, ZHOU Yan, ZHU Kuanliang, WANG Zaiming
2020, 48(6): 8-14.   doi: 10.11911/syztjs.2020090
[Abstract](226) [FullText HTML](48) [PDF 1058KB](77)
Abstract:
In order to solve the technical difficulties of sidetracking with ϕ139.7 mm casing in shallow horizontal wells of the Jidong Oilfield, which included high pumping pressure, low ROP, poor oil-water layers isolation effect, and rapid rise of water cut after the oil well was put into production, etc., many countermeasures were taken. Those technologies include adoption of ϕ79.4 mm non-standard drill pipe to lower the mud pump, adoption of a small size hydraulic pressurization and speed-up tool that can flexibly pressurize the drill bit to increase the ROP, selection of ϕ95.3 mm non-standard casing, adoption of the top cementing completion with expansive suspension liner and screen liner, and formulation of technical measures to improve the cementing quality of slim hole sidetracking. The key technologies for drilling and completion of shallow slim hole sidetracked horizontal wells in the Jidong Oilfield was thus formed. These technologies were tested in 5 shallow sidetracking horizontal wells with high water-cut in the Jidong Oilfield. Compared with adjacent wells without adoption of these technologies, the pumping pressure was effectively controlled, the ROP was increased by 24.6%, the drilling cycle was shortened by 14.1%. At the same time, the poor sealing problem of the slim hole with a narrow gap was solved, and the isolation of the aquifers in horizontal section and seal of the sidetracking window was achieved, by which the impact on the later oil production was avoided. The test results showed that the proposed key technologies could effectively increase the ROP in the slim hole sidetracking in horizontal wells, shorten the drilling cycle and isolate oil and water layers. With good effect in speed-up and efficiency improvement, the technologies have a high potential for popularization and application.
One-Trip Drilling Technology of the Second-Spud Section for Slim-Holes in the Southern Sulige Block
SHEN Zhaochao, HUO Rujun, YU Yanfei, DONG Yifan, NI Xiaowei, LEI Yu
2020, 48(6): 15-20.   doi: 10.11911/syztjs.2020081
[Abstract](170) [FullText HTML](31) [PDF 692KB](70)
Abstract:
In order to further enhance the penetration rate of slim holes in the Southern Sulige Block and reduce the development cost, technical research on the one-trip drilling technology of the second-spud section has been carried out. For this purpose, by means of bit modification, the bit teeth arrangement and streamline designs were optimized to enhance the bit stability and abrasion resistance. The positive displacement motor (PDM) design was optimized to prolong the service life and output power of PDM. The drilling parameters were optimized to realize an aggressive drilling and improve the rock breaking efficiency of bit. The BHA was optimized and the well trajectory was reasonably adjusted to ensure that the drilling of the long hold section and drop section could be fulfilled in one trip. Tests of one-trip technology of the second-spud section were carried out on two slim holes at SN00XX platform. Among these wells, Well SN00XX-02 achieved one-trip drilling of the second-spud section with the PDM. Well SN00XX-04 achieved one-trip drilling of both the PDM and the bit in the second-spud section. The technology of one-trip drilling was successfully applied in other two wells, and the drilling cycles were shortened by 7.6%. The research results showed that one-trip drilling technology could effectively implemented in the second-spud section, with remarkable improved penetration rate, which provided a technical support for the follow-up rapid drilling of slim-holes in the Southern Sulige Block.
High-Performance Oil-Based Drilling Fluid Technology for Horizontal Wells in the Madong Oilfield, Junggar Basin
ZHANG Xiong, YU Jin, MAO Jun, LIU Zulei
2020, 48(6): 21-27.   doi: 10.11911/syztjs.2020106
[Abstract](163) [FullText HTML](44) [PDF 850KB](43)
Abstract:
The build-up section and horizontal section drilling in horizontal wells of the Madong Oilfield, Junggar Basin was challenged by problems such as pipe-string sticking during trip operations, wellbore instability, and low ROP caused by the hydration of mudstone, abnormal pressure, and an abundance of glutenites. Therefore, high-performance oil-based drilling fluid was accordingly investigated. Based on the reservoir characteristics of the Madong Oilfield and the drilling requirements of the medium-long horizontal sections, XZ high-performance oil-based drilling fluid was hereby formulated, and indoor laboratory experiments were carried out to evaluate its weighting, temperature resistance, shear strength improving, sealing/pressure-bearing, anti-pollution and anti-freezing performances. The results showed that this oil-based drilling fluid system exhibited stable rheological properties and an adjustable shear force between the density of 1.35–2.01 kg/L. The new fluid exhibited good thermal and freezing stability, low temperature resistance of up to –24 ℃, and high temperature resistance of up to 180 ℃. The emulsification stability was good, and the demulsification voltage was generally above 1 000 V. The anti-pollution ability was strong, the anti-cuttings pollution concentration was ≥20.0%, the anti-formation water pollution concentration was ≥20.0%, and the anti-cement pollution concentration was ≥10.0%. Further, the new drilling fluid system had strong sealing ability. When using sand discs with a diameter of 120 and 150 μm for pressure-bearing sealing, the pressure-resistance of both discs could reach 15 MPa. This system was applied in 4 of the wells in the Madong Oilfield. After the application of the new fluid, perfect borehole stability was achieved, the hole enlargement rate of the build-up section was only 3.55%, the trip operation was completed smoothly, and the average ROP was 79.0% higher than that of the same horizon drilled with water-based drilling fluid. A remarkable drilling speed-up effect was observed. The research results showed that the application of XZ high-performance oil-based drilling fluid can solve the technical problems in the development of the glutenite reservoirs in the Madong Oilfield and satisfy the needs of safe and fast drilling in the long horizontal section of this oilfield.
Study of the Rheological Properties of High-Density Oil-Based Drilling Fluid Considering Wall Slip Effect
LI Wenzhe, ZHONG Chengxu, JIANG Xuemei, LI Zhengtao, CAO Shiping, WU Shuang
2020, 48(6): 28-32.   doi: 10.11911/syztjs.2020085
[Abstract](137) [FullText HTML](45) [PDF 980KB](40)
Abstract:
Wall slip effect seriously affects the accurate measurement of the rheological properties of high-density oil-based drilling fluids, and it needs careful detection and correction. A correction method for the wall slip effect during the measurement of the rheological properties of high-density oil-based drilling fluids was established based on the Tikhonov regularization method. Rheological property measurement experiments of high-density oil-based drilling fluids in deep shale gas wells considering wall slip effect were carried out using a six-speed rotational viscometer, and the wall slip characteristics of high-density oil-based drilling fluids were analyzed. The rheological model was optimized and the rheological parameters were calculated. The calculation results demonstrate that, when compared with the rheological parameters before correction, the dynamic shear force of high-density oil-based drilling fluids in deep shale gas wells is reduced after correction, while the liquidity index is increased to nearly 1.00. The results demonstrate the real rheological properties can be expressed by Bingham model. When the wall shear stress is higher than the critical shear stress, the slip velocity will increase exponentially with increasing wall shear stress.The results show that a slip effect exists during the measurement of the rheological properties of high-density oil-based drilling fluids. It demonstrates, too, that the rheological model and rheological parameters before and after slip correction are significantly different, and the influence of slip effect should be eliminated for accurate measurement.
Anti-Leakage Cementing Technology for the Long Well Section below Technical Casing of Ultra-Deep Wells in the No.1 Area of Shunbei Oil and Gas Field
YANG Hongqi, SUN Lianhuan, AO Zhuqing, SANG Laiyu, YANG Guangguo, GAO Yuan
2020, 48(6): 33-39.   doi: 10.11911/syztjs.2020110
[Abstract](157) [FullText HTML](32) [PDF 865KB](56)
Abstract:
With a goal of overcoming cementing challenges encountered in drilling the section below technical casing in the No.1 Area of the Shunbei Oil and Gas Field, an anti-leakage cementing technology for long-sealing section was studied. Problems to be overcome included low pressure-bearing capacity of Silurian strata, serious leakage, long sealing section of primary cementing and high leakage rate. Causes were analyzed from geological and engineering aspects, and technical requirements were clarified. High strength hollow glass microspheres were selected as the weight reducer, and a low-density cement slurry was developed based on particle grading principle. Fibers of different sizes in the isolation fluid were used to improve the pressure bearing capacity of formation. In addition, a“normal injection and reverse squeezing”anti-leakage cementing technique was developed to optimize the performance of the liner cementing of long sealing section in ultra-deep wells. The results of laboratory tests show that the density increase of low-density cement slurry was less than 0.03 kg/L under 100 MPa. The cement stone had a good pressure bearing capacity and compressivestrength, which was over 15 MPa. The pressure-bearing capacity of formation was increased by 1.5 MPa by using an anti-leakage spacer fluid. An anti-leakage cementing technique for the long sealing well section below the technical casing in the ultra-deep wells in the No.1 Area of the Shunbei Oil and Gas Field is formed by the combination of“normal injection and reverse squeezing”cementing process, low-density cement slurry, and plugging-type spacer fluid. This technology has been applied in the ϕ177.8 mm liner cementing jobs in more than 10 wells with annulus of those wells thoroughly sealed by cement slurry without leakage section, by which the cementing leakage problem was solved. The results of research and applications show that this technology has achieved a significant anti-leakage effect, and it can effectively solve the cementing problems in this area.
Research and Application of Tough Cement Slurry Systems with Multi-Scale Fiber
ZOU Shuang, FENG Minghui, ZHANG Tianyi, ZOU Jianlong, ZENG Jianguo, ZHAO Baohui
2020, 48(6): 40-46.   doi: 10.11911/syztjs.2020084
[Abstract](127) [FullText HTML](34) [PDF 909KB](45)
Abstract:
To solve the problems of high brittleness, low tensile strength, poor impact resistance and fracture resistance of the cement stone in oil wells, a multi-scale fiber toughener BCE-230S was formed by selecting inorganic fibers in three different scales and conducting orthogonal tests for compound. In addition, the effects of the dosage of BCE-230S on the construction performance of cement slurry and the mechanical properties of cement were investigated, the optimal dosage was determined, by which a tough cement slurry system with multi-scale fiber was formed. The results showed that the splitting tensile strength, compressive strength and impact resistance of the cement stone were significantly improved when compared with common cement.Young’s modulus decreased significantly and the construction performance was ideal. The tough cement slurry system with multi-scale fiber was applied in the low permeability reservoir in the Jidong Oilfield for more than 10 times in the well, and the cementing quality of the two cementing surfaces was measurably improved compared with that of adjacent wells. Fracturing in later stage was successful, and no fluid channeling was observed during well testing. The results indicated that the tough cement slurry system with multi-scale fiber can effectively solve the problem of brittleness of cement stone in oil well, so as to ensure the integrity of the wellbore and the long-term cementing quality, with a potential for wide application.
Research on Drilling Tool Wear and Anti-Wear Technology for Hot Dry Rock Drilling
WANG Heng, WANG Lei, ZHANG Dongqing, ZHANG Jinshuang
2020, 48(6): 47-53.   doi: 10.11911/syztjs.2020099
[Abstract](158) [FullText HTML](33) [PDF 1344KB](41)
Abstract:
In order to clarify the wear mechanism of drilling tools during hot dry rock drilling and propose an appropriate anti-wear technical scheme to alleviate the wear of drilling tools, the motion state of drilling string in the wellbore was first analyzed and the contact relationship between the drilling string and the sidewall was described. Furthermore, the finite element method was used to establish a model for analyzing the drilling string dynamics. Later, by taking the drilling of a typical hot dry rock well as an example, the contact state between the drilling tool and the sidewall was analyzed by solving the dynamic model of the drilling string. Finally, with the goal of reducing the contact force between drilling tool and sidewall, the influence law of BHA (bottom hole assembly) and drilling parameters on the dynamic characteristics of drilling tools were analyzed. In addition, the recommended anti-wear technical scheme of BHA and drilling parameters was proposed through the optimization of BHA and drilling parameters. The technical scheme was then tested and applied in on-site hot dry rock drilling. After drilling 116.00 m, the stabilizer was worn by only 3.0 mm, indicating that a good anti-wear effect was obtained. This technical scheme can provide a new solution to alleviate drilling tool wear in hot dry rock drilling.
Experimental and Numerical Study of the Explosive Forming of Slotted Metal Pipes for Energy-Gathered Nesting Plugging
ZHANG Yiqun, YU Chao, CHENG Guangming, SONG Xianzhi, ZHAO Kexian
2020, 48(6): 54-60.   doi: 10.11911/syztjs.2020107
[Abstract](136) [FullText HTML](27) [PDF 1206KB](28)
Abstract:
At present, there is still no effective solution to the cavity-type lost circulation in the drilling and completion of oil, gas and geothermal resources. In the light of this, a energy-gathered nesting plugging technique was proposed, and experiments for explosive forming and the optimization of metal bridge strings were also conducted. The technique and its theory were first introduced, a numerical model for the explosive forming of slotted metal pipes was then established, the shapes of metal pipes slotted in different types and in different materials were analyzed. Finally, ground experimental device was designed, the experimental methods were determined, and according to the simulation results, ground experiments were conducted in air, submerged water, and submerged confining environments respectively. The numerical results show that the series 5 aluminum alloy pipe with straight slotting patterns, exhibits a suitable tensile deformation without failure after explosion, and can be utilized as the material for nesting bridge. The experimental device can effectively simulate the real downhole environment, providing conditions for further study on the the amount of explosives of different nesting tools. The research results show that the energy-gathered nesting plugging technology could be expected to better solve the technical problems that the plugging materials are difficult to retain and not easy to form the artificial well wall. By using it, the success rate of plugging of cavity-type lost circulation could be improved and the cost of drilling and completion could be reduced.
Integrated Fishing and Reaming Technology for Downhole Large-Diameter Collapsed Objects
QIN Chun, CHEN Xiaoyuan, CHENG Zhiyong
2020, 48(6): 61-64.   doi: 10.11911/syztjs.2020088
[Abstract](121) [FullText HTML](41) [PDF 1894KB](52)
Abstract:
Fissured deep mudstone formation and fractured formation are prone to collapse during drilling, and the size of collapsed objects are large. Resistance is encountered while dealing with downhole large-diameter collapsed objects by using conventional methods such as “slug” sweep, and reaming with cone bit and reverse circulation junk basket. It is time consuming and seriously affects the drilling cost and benefit. Based on the analysis of the reasons why it is difficult and time consuming to handle large-diameter collapsed objects by conventional methods, a drilling tool integrating breaking, reaming and fishing was developed. In addition, different parameters of reaming and fishing, and techniques for removing collapsed objects were adopted according to downhole conditions. Therefore, an integrated processing technology of fishing and reaming for downhole large-diameter collapsed objects was formed. The technology was applied in 12 wells encountering resistance adopted reaming due to downhole collapse, and achieved a 100% success rate in reaming and fishing. The results suggested that this technology could bring about integrated reaming and fishing for large-diameter collapsed objects in downhole hard-brittle mudstone. Further, this process had a positive effect on the quick treatment of large-diameter collapsed objects in downhole hard-brittle mudstone, and could effectively reduce the time for handling downhole failures.
Design and Implementation of a Downhole Safety Monitoring System
ZHANG Zhiliang, WANG Wei, YI Ming, LIU Qiang
2020, 48(6): 65-70.   doi: 10.11911/syztjs.2020094
[Abstract](174) [FullText HTML](44) [PDF 1112KB](42)
Abstract:
In order to solve the problems of frequent downhole safety accidents, low early-warning efficiency, lagging safety monitoring technology in China, a downhole safety monitoring system with independent intellectual property rights was designed and developed. This system directly measures near-bit mechanical parameters and engineering parameters, and transmits the measured parameters to the drilling risk analysis and assessment module in real time by using the drilling fluid pulse, by which the received data can be analyzed and calculated to determine the type of drilling risk and assess the risk level. Field tests confirmed that the downhole safety system is fully functional and has a stable performance. The accuracy rate of the risk assessment is higher than 95%, and some technical indexes have reached the level of similar monitoring system abroad. The research show that the downhole safety monitoring system could reduce the drilling risk and drilling cost in deep complex formations. It could create great economic benefits for it has solved the problem of low early warning efficiency of downhole safety accidents.
Development and Testing of a Graphene-Modified Sponge Coring Tool
CHEN Zhongshuai, WU Zhonghua, SI Yinghui
2020, 48(6): 71-75.   doi: 10.11911/syztjs.2020111
[Abstract](149) [FullText HTML](45) [PDF 878KB](25)
Abstract:
In order to directly measure and accurately obtain the oil saturation of cores, processes such as graphene gel impregnation, aging and supercritical drying were used in conjunction with a conventional sponge to obtain the graphene sponge material with an adjustable pore diameter. At room temperature, crude oil absorption of graphene sponge material is as high as 80.5 times its own mass, and the graphene modified sponge coring tool is designed and developed. The grapheme modified sponge coring tool adopts pre-filled sponge protection fluid and a sealed piston to protect the sponge material from being polluted. Through indoor laboratory experiments, the diameter of sponge liner is determined to be 0.6–1.0 mm less than that of the core, and a strip sheet is used to press and protect the sponge liner while satisfying the requirement of oil absorption and core feeding. Based on the comparison with conventional methods, the measurement and calculation methods of the oil saturation of cores are determined. This new sponge coring tool can effectively collect the crude oil escaping from the core without compromising the core recovery. Therefore, it demonstrates a high potential for application.
The Development and Field Testing of a High-Temperature Deep-Layer Open Hole Packer for Acid Fracturing Completion in Deep Carbonate Reservoirs
LIU Yang
2020, 48(6): 76-81.   doi: 10.11911/syztjs.2020044
[Abstract](351) [FullText HTML](149) [PDF 964KB](48)
Abstract:
Premature aging of packer rubber elements and damage-prone of packer skeletons during the open hole well completions have been a problem in the deep Ordovician reservoirs of Northern Tarim Basin. To solve this, the causes of failures have been analyzed, after which a flexible anchor slip structure was designed for the protection of steel skeleton and prevention of damage to the rubber element caused by the excessive deformation of steel skeleton under large expansion ratio and high pressure. While maintaining the excellent aging resistance of fluororubber, plasticizing modification technology was used to improve its plasticity and thermal stability, which would make it easier to be moulded through mold injection. For the fluid inlet channel of the setting mechanism, a ball-activated protective sliding sleeve was designed to avoid the settling and clogging of drilling fluid. The improved open hole packer had a temperature resistance of 180 ℃ and strong sealing capacity, which was suitable for long-term sealing of irregular open hole formations. When applying such improved open hole completion packer in 4 wells in the Halahatang Area of Northern Tarim Basin, the RIH was smooth, the setting sign was obvious, and there was no abnormal casing pressure during the large-scale acid fracturing and production process. Research results showed that the improved packer met the needs of the integration of completion, acid fracturing and production testing, solved problems of deep oil and gas development in Tarim Basin, and had a good value for popularization and application.
Oil & Gas Exploitation
Research and Test on the Stimulated Reservoir Volume Technology of Hot Dry Rock
CHEN Zuo, ZHANG Baoping, ZHOU Jian, LIU Honglei, ZHOU Linbo, WU Chunfang
2020, 48(6): 82-87.   doi: 10.11911/syztjs.2020098
[Abstract](88) [FullText HTML](39) [PDF 1075KB](35)
Abstract:
Compared with conventional oil and gas resources, the lithology, mechanical properties, development and utilization methods for simulating reservoir volume in hot dry rock are quite different. The fracturing technologies for shale and tight sandstone cannot be directly used in hot dry rocks, and it is necessary to study a fracturing technology that is suitable for the stimulation of hot dry rock. To this end, the mechanical properties of rocks under high-temperature conditions were tested and analyzed by using downhole granite cores and large-size outcrop samples. By adopting high-temperature testing and true tri-axial physical simulation systems, it was possible to simulate and study the morphological characteristics of crack initiation and propagation. The characteristics of brittle-plastic granite at high temperature, rock failure features and the effect of natural fractures on the fracture pressure, propagation path and morphology were analyzed. On this basis, a stimulated reservoir volume technology of low flowrate thermal fracture + gel expanding of cracks + variable flowrate cyclic injection was proposed. A pilot fracturing program at well site was conducted to verify the results of indoor research. Studies suggested that granite had a strong plasticity, poor brittleness, and a large horizontal stress difference at high temperatures. The rock is mainly damaged by tension-shear failure, and natural fractures and temperature difference effect can significantly reduce the fracture pressure, increase the complexity of fractures and achieve a stimulated reservoir volume. The research results can provide a good guidance and best practices for the efficient development of hot dry rock reservoirs.
An Experimental Study on Evaluation Methods for Fracturing Effect of Fractured-Vuggy Carbonate Reservoir
LI Xinyong, GENG Yudi, LIU Zhiyuan, WANG Wenzhi, ZHOU Zhou
2020, 48(6): 88-93.   doi: 10.11911/syztjs.2020074
[Abstract](76) [FullText HTML](42) [PDF 959KB](22)
Abstract:
The lack of evaluation system for evaluating communication of fractures in vuggy carbonate reservoirs makes it impossible to quantitatively analyze post frac treatment. Therefore, it is necessary to establish an evaluation method for post frac according to the characteristics of abundant natural fractures and karst caves in carbonate reservoirs. A physical experiment simulated hydraulic fracturing on artificial fractured-vuggy carbonate cores was conducted, the evaluation criteria that meets the fracturing characteristics of fractured-vuggy carbonate reservoirs were proposed based on the experimental results, and the concept of fractured-vuggy communication coefficient was proposed. Then, the proposed coefficient was used to quantitatively analyze the influence of in-situ differential stress on vuggy carbonate fracturing effect. The experimental results show that the SRV coefficient used to evaluate fracturing effect cannot accurately evaluate the effect of fractured-vuggy carbonate fracturing, while the fractured-vuggy communication coefficient can make a more accurate evaluation. The influence of horizontal in-situ differential stress on fractured-vuggy carbonate fracturing effect was evaluated with the proposed coefficient. It is found that the coefficient decreases first then increases with the increase of in-situ differential stress. The results demonstrate that the influence of various factors on fracturing effect of fractured-vuggy carbonate reservoirs are different from that of conventional ones, and the proposed fractured-vuggy communication coefficient can be used to more precisely analyze the fracture propagation and communication conditions, and to more effectively evaluate such reservoirs.
Segmented Multi-Cluster Fracturing Technology for Sidetrack Horizontal Well with Slim Holes in Low Permeability Reservoir
SU Liangyin, CHANG Du, YANG Haien, DUAN Penghui, XUE Xiaojia, BAI Jianwen
2020, 48(6): 94-98.   doi: 10.11911/syztjs.2020112
[Abstract](81) [FullText HTML](12) [PDF 1025KB](33)
Abstract:
Owing to the failure of improving single well productivity due to the problem that segmented fracturing can’t be effectively conducted in horizontal well with ϕ88.9 mm hole sidetracked by using the old wellbore in water flooding low permeability sandstone reservoir, numerical simulation method is used to simulate the influence of different fracture density and number of fracturing sections on oil well productivity and water cut based on the well pattern arrangement and remaining oil distribution characteristics. The laboratory simulation and field test result show that when the fracture density is 4–6 per 100 m and the fracture length is 100–120 m, the effect of water control and oil increase is better. The effective separation of each fracturing section in horizontal section of slim hole can be fulfilled and the efficiency can be improved by using segmented multi-cluster fracturing technology with soluble bridge plug technology and pony packer pipe strings. Successful practice of segmented multi-cluster fracturing technology in slim hole sidetracking horizontal well provides the technical support for low permeability reservoir to recover single well productivity and to improve ultimate oil recovery.
Evaluation on the Production Effect of Coiled Tubing in Fuling Shale Gas Field
LIU Yaowen, LI Mu
2020, 48(6): 99-103.   doi: 10.11911/syztjs.2020089
[Abstract](100) [FullText HTML](28) [PDF 1093KB](40)
Abstract:
Coiled tubing (CT) is widely used in the Fuling Shale Gas Field as a gas production string, and its specifications are mainly ϕ50.8 mm×4.45 mm and ϕ38.1 mm×3.68 mm. The production effect of CT in different shale gas wells are different. For the goal involved analyzing the reasons for the differences and improving the application effect of CT in shale gas wells, based on the field applications, the production effect of CT was evaluated from the perspectives of shale gas well liquid carrying effect, wellbore pressure loss and stable production capacity of gas wells. Further, the influences of CT diameter, setting depth and setting timing on CT production effect were analyzed. The results showed that the critical liquid carrying capacity could be reduced by 38% using ϕ50.8 mm×4.45 mm CT rather than the ϕ60.3 mm×4.83 mm conventional tubing. The water gas ratio had a significant influence on the production effect of coiled tubing. The larger water gas ratio, the CT diameter and setting depth could more significantly influence the wellbore pressure loss and gas well stable production time. For shale gas wells with a water gas ratio of 0–1.5 m3/104m3 the earlier the ϕ50.8 mm×4.45 mm CT was set, the longer the stable flow production period, and the higher the cumulative gas production in the flow production period. The research demonstrated that the application of CT could achieve the continuous and stable production of shale gas wells with low water gas ratio, and the result could play a guiding role in improving the application effect of CT in Fuling Shale Gas Field.
Simulation Tests of Effective Stress Changes in Gas Storage during Injection and Production
YOU Lijun, SHAO Jiaxin, GAO Xinping, KANG Yili, WANG Furong
2020, 48(6): 104-108.   doi: 10.11911/syztjs.2020102
[Abstract](60) [FullText HTML](10) [PDF 1350KB](20)
Abstract:
The change of effective stress in the periodic injection-production process of underground gas storage will cause stress sensitivity of the reservoir. In order to understand the influence of stress sensitivity on permeability of gas storage reservoir and to provide the basis for optimizing the injection and production system of gas storage, stress sensitivity tests with consideration of effective stress action duration and without were carried out on carbonate rock samples, and the permeability of the rock samples in the test process were tested. By means of scanning electron microscope (SEM), the fracture wall of rock samples before and after the test considering the effective stress action duration was observed. The test results show that the stress sensitivity of carbonate fractures and matrix rock samples is weak–moderately weak and none without consideration of action duration, while the stress sensitivity of fracture and matrix rock samples considering the effective stress action duration is moderately strong–strong and weak. With the increase of effective stress action duration, the breaking of micro-protrusions on rock fracture walls and the initiation and propagation of micro-fractures will strengthen the stress sensitivity of rock samples. The results show that for the purpose to weaken the stress sensitivity of underground gas storage, the injection-production pressure of underground gas storage should be controlled reasonably.
Well Logging & Surface Logging
Development and Testing of a Portable Acoustic Logging System on Cuttings
WANG Zhizhan, ZHU Zuyang, LI Fengbo, ZHANG Yuanchun, ZHANG Wei, DU Huanfu
2020, 48(6): 109-115.   doi: 10.11911/syztjs.2020141
[Abstract](111) [FullText HTML](32) [PDF 1055KB](49)
Abstract:
In order to measure the real-time acoustic velocity in the formation while drilling, a portable acoustic logging system on cuttings with high precision was developed based on the research of acoustic logging on cuttings. In the design of this logging system, integrated circuit of pulse generator and oscilloscope was adopted. In addition, software functioning as oscilloscope that could quickly read and store waveform data was studied for this system. By using the ultrasonic transmission method, an ultrasonic probe was used to emit ultrasonic waves with 1 MHz frequency to measure the P-wave velocity and S-wave velocity of the acoustic wave passing through cuttings samples. Results comparisons were conducted on both the laboratory test and the dipole acoustic logging in actual drilling. The results showed that the accuracy of acoustic velocity measurement was more than 98.0%, and the consistency of acoustic logging data of cuttings and wireline acoustic data was greater than 80.0%. This system could not only be used to monitor abnormal formation pressure while drilling, but also to evaluate rock brittleness, compressibility, drillability and wellbore stability in real time.
Logging Evaluation on the Effectiveness of Karst Fractured-Vuggy Reservoirs in the Maokou Formation, Sichuan Basin
ZHANG Feng, LUO Shaocheng, LI Zhen, MU Yu, LI Tingting
2020, 48(6): 116-122.   doi: 10.11911/syztjs.2020140
[Abstract](62) [FullText HTML](6) [PDF 962KB](27)
Abstract:
Logging evaluation was carried out to solve the problems of high levels of heterogeneity, complexity with respect to typing reservoir spaces, and difficulty in evaluating the reservoir effectiveness in carbonate reservoirs in the Maokou Formation, Sichuan Basin. By analyzing the pore structure of the fractured-vuggy reservoirs of the Maokou Formation in the working area, the reservoir space was classified based on the tri-porosity model and the relationship between bond index and total porosity, connected fracture-vug porosity and isolated fracture-vug porosity. The information was then combined with core calibration logging, the mean value and variance of apparent porosity spectrum and apparent formation water resistivity spectrum extracted from micro-resistivity scan imaging logging data, and fracture porosity and other sensitive parameters that reflect pores, vugs and fractures, as well as the data from well testing. Integrating above information, and evaluation standard for reservoir effectiveness was established as follows: For porous and vuggy reservoirs, the mean value of electric imaging apparent porosity spectrum of Class I reservoir is greater than 1.9 and the corresponding variance is greater than 1.2, and those of Class II reservoirs are greater than 1.7 and 0.9, respectively. For fractured reservoirs, the fracture porosity of Class I reservoir is greater than 0.30 while that of Class II reservoir is between 0.05 and 0.30. Enhancing the connectivity of fractures can obviously improve the effectiveness of the reservoir. For the porous-fracture and vuggy-fracture reservoirs, the mean value of apparent formation water resistivity spectrum of Class I reservoir is greater than 700, and the variance is greater than 300, and those of Class II reservoirs are 500–700 and 100–300, respectively. According to the evaluation standard, a secondary interpretation of 20 exploration wells in the working area was carried out, which effectively improved the interpretation coincidence rate of fractured-vuggy reservoirs, and resulted in achieving a good application effect.
Drilling Technology Challenges and Resolutions in Fuling Shale Gas Field
Niu Xinming
2014, 42(4): 1-6.   doi: 10.3969/j.issn.1001-0890.2014.04.001
[Abstract](5528) [PDF 1006KB](4011)
The Key Drilling Technologies in Fuling Shale Gas Field
Ai Jun, Zhang Jincheng, Zang Yanbin, Xu Mingbiao
2014, 42(5): 9-15.   doi: 10.11911/syztjs.201405002
[Abstract](4244) [PDF 1084KB](4023)
Large-Scale Multi-Stage Hydraulic Fracturing Technology for Shale Gas Horizontal Well JY1HF
Zhou Dehua, Jiao Fangzheng, Jia Changgui, Jiang Tingxue, Li Zhenxiang
2014, 42(1): 75-80.   doi: 10.3969/j.issn.1001-0890.2014.01.015
[Abstract](6113) [PDF 1149KB](4176)
Application of Multi-Well Pad in Unconventional Oil and Gas Development in China
Zhang Jincheng, Sun Lianzhong, Wang Jiachang, Zang Yanbin
2014, 42(1): 20-25.   doi: 10.3969/j.issn.1001-0890.2014.01.004
[Abstract](4717) [PDF 1211KB](4006)
Integration Technology of Geology Engineering for Shale Gas Development
Zeng Yijin
2014, 42(1): 1-6.   doi: 10.3969/j.issn.1001-0890.2014.01.001
[Abstract](4420) [PDF 1065KB](4478)
A New Method for Evaluating Shale Fracability Index and Its Application
Jiang Tingxue, Bian Xiaobing, Su Yuan, Liu Shuanglian, Wei Ran
2014, 42(5): 16-20.   doi: 10.11911/syztjs.201405003
[Abstract](3817) [PDF 1055KB](3678)
Status and Prospect of Multi-Well Pad Drilling Technology in Shale Gas
Chen Ping, Liu Yang, Ma Tianshou
2014, 42(3): 1-7.   doi: 10.3969/j.issn.1001-0890.2014.03.001
[Abstract](4024) [PDF 1031KB](3977)
Development and Pilot Test of Hydro-Oscillator
Li Bo
2014, 42(1): 111-113.   doi: 10.3969/j.issn.1001-0890.2014.01.022
[Abstract](3921) [PDF 1085KB](4073)
Evaluation Model for Shale Brittleness Index Based on Mineral Content and Fracture Toughness
Liao Dongliang, Xiao Lizhi, Zhang Yuanchun
2014, 42(4): 37-41.   doi: 10.3969/j.issn.1001-0890.2014.04.007
[Abstract](3773) [PDF 1143KB](3731)
Development and Reflection of Oil-Based Drilling Fluid Technology for Shale Gas of Sinopec
Lin Yongxue, Wang Xianguang
2014, 42(4): 7-13.   doi: 10.3969/j.issn.1001-0890.2014.04.002
[Abstract](4052) [PDF 1031KB](3636)