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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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Key Drilling Techniques of High Temperature and High Pressure Horizontal Wells in the Middle and Deep Layer of the Eastern Area of Yinggehai Basin, South China Sea
WU Jiang, LI Yanjun, ZHANG Wandong, YANG Yuhao
 doi: 10.11911/syztjs.2019112
[Abstract](58) [FullText HTML](34) [PDF 1017KB](2)
Abstract:
In view of the problems of high difficulty, high risk and little experience in drilling horizontal well of high temperature and high pressure gas reservoir in the middle and deep layer of Yinggehai Basin, South China Sea, which limits the development capacity of high temperature and high pressure gas field, the technical difficulties and risks are analyzed. The well structure design, domestic oil-based drilling fluid, micron grade barite weighting, high-efficiency flushing fluid, wear and CO2 corrosion factors are considered. The key technologies of high temperature and high pressure horizontal well drilling have been formed through the application of more than ten wells on site. Through the application of the above technology, the average drilling efficiency of the completed high temperature and high pressure horizontal well is 95%, the drilling efficiency is significantly improved compared with the design, and the blowout production capacity is 30% higher than expected. The practice results show that the application effect of high temperature and high pressure horizontal well drilling technology is good, which can provide important technical support for the follow-up large-scale development and production capacity construction of high temperature and high pressure gas field in South China Sea.
Study and Test of the Energy Storage Fracture in the Horizontal Wells in Ultra-Low Permeability Reservoir
HUANG Ting, SU Liangyin, DA Yinpeng, YANG Li'an
 doi: 10.11911/syztjs.2020024
[Abstract](28) [FullText HTML](14) [PDF 982KB](6)
Abstract:
The problem of low productivity and low efficiency of some horizontal wells in ultra-low permeability reservoirs was presented after a period of production. The research and experiment on refracturing stimulation of horizontal wells in ultra-low permeability reservoirs was carried out. According to the failure mechanism of rock, the simulated energy storage fracturing experiment was carried out. The damage of the internal friction of the specimen was detected by acoustic emission signal. At the same time, the finite element method is used to calculate the change of ground stress in the near-well zone. The test proves that under the action of high pore pressure, the traces of natural crack surface are obvious. During the rolling process, a large number of micro-ruptures are generated inside the specimen. The geostress field after a period of fracturing is affected in the post-pressing well, The research results show that before the refracture, an appropriate amount of oil-displacement fracturing fluid is injected, and the well can be used for infiltration and diffusion, which can effectively supplement the formation energy. At the same time, combined with the optimized volumetric refracturing technology, the volume and complexity of the crack transformation can be further improved. The technology has good adaptability to the production of low-yield horizontal wells caused by energy deficit and crack closure, and provides reference for refracturing of similar ultra-low permeability reservoirs.
Modeling of Wellbore Collapse Pressure for Shale Gas Formation based on Coupling with Mechanics and Chemistry
DENG Yuan, HE Shiming, DENG Xianghua, PENG Yuanchun, HE Shiyun, TANG Ming
 doi: 10.11911/syztjs.2020010
[Abstract](175) [FullText HTML](74) [PDF 2328KB](3)
Abstract:
At present, the development of shale gas is mainly based on horizontal wells and large-scale volume fracturing. The wellbore instability under the conditions of water-based drilling fluids has always been one of the technical bottlenecks which constrains the safe and economic development of shale gas. In the analysis of the wellbore stability of shale gas horizontal wells coupling with mechanics and chemistry, most of them have only considered the effect of hydration on rock strength, but rarely have considered the effect of hydration strain stress. Based on the theories of elastic and rock mechanics and considered the hydration effect on the rock strength and the additional hydration stress, this paper establishes a predictive model of wellbore collapse pressure for shale gas formation based on coupling with mechanics and chemistry, and analyzes the mechanism of horizontal shale gas wellbore instability and the influence of main factors on wellbore stability. The results show that the collapse density increases significantly with bedding plane; when drilling direction near the bedding plane surface orientation, the wellbore stability is the best; when the hydration time is constant, the collapse pressure decreases with the increase of radial distance; the longer the drilling time is, the larger area near the wellbore easily collapsed is; After considering the influence of hydration stress, the collapse density is greatly increased. When designing the drilling fluid density, the influence of hydration stress cannot be ignored. The research results have enriched the theory of shale gas horizontal wellbore instability, which has a important guidance for the safe and efficient development of shale gas horizontal wells.
Long Openhole Cementing Technology for Well SBY-1 Drilled with a ϕ444.5 mm Bit
ZOU Shuqiang, WANG Jianyu, ZHANG Hongwei, Eerqm
 doi: 10.11911/syztjs.2020008
[Abstract](89) [FullText HTML](26) [PDF 695KB](4)
Abstract:
In the second spud of shunbeiying 1 well, the ϕ444.5 mm drill bit is used to drill to the depth of 5 395.00 m, and put in the ϕ339.7 mm technical casing. There are a series of technical problems in casing running and cementing operation, such as heavy casing suspension, long open hole section, development of leakage layer of Permian igneous rock, lack of experience in running super deep and large-scale graded cement injector, etc., which are very easy to cause complex working conditions such as sticking in casing running and loss of return in cementing. Therefore, it is urgent to optimize the matching technology to ensure the cementing quality. According to the special working conditions of shunbeiying 1 well, through load checking calculation, well passing measures strengthening, casing running speed and drilling fluid performance optimization, a large-scale casing running technology of ultra deep well is formed; through discontinuous staged cement injection technology and low-density leak proof cement slurry system optimization, the cementing technology of ultra deep and large-scale casing is improved. Based on the above measures, the second spud in casing of shunbeiying 1 well is running smoothly, and the acoustic amplitude of easily lost zone is less than 30%, which realizes effective sealing. The research results can be used for reference for large-scale casing running and cementing construction in ultra deep wells, and effectively ensure the safe and efficient development of Shunbei block.
Simulation to Determine Depth of Detection and Response Characteristics while Drilling of an Ultra-Deep Electromagnetic Wave Instrument
HUANG Mingquan, YANG Zhen
 doi: 10.11911/syztjs.2019132
[Abstract](219) [FullText HTML](21) [PDF 1302KB](7)
Abstract:
Studying the boundary detection depth while drilling for different antenna combinations is the primary objective of developing ultra-deep electromagnetic wave instruments. The numerical simulation method has been used to study the boundary detection depth and response characteristics of three kinds of receiving antennas: axial antenna, horizontal antenna and tilted antenna. The simulation analysis suggested that the detection depth while drilling for the ultra-deep electromagnetic wave instrument was related to the coil spacing, operating frequency and the formation resistivity contras. Further, it became clear that different electromagnetic field components had different response characteristics to the formation interface, and the axial resistivity measurement of ultra-deep detector was more likely to be affected by adjacent layers than the conventional electromagnetic waves. When the horizontal antenna was used, the smaller the coil spacing and the higher the operating frequency, the larger the potential signal amplitude of directional electromotive force.; Then, when the tilted antenna was used, the larger the coil spacing and the higher the operating frequency, the larger the potential relative directional signal amplitude. While using the ultra-deep electromagnetic wave instrument while drilling, the coil spacing should be small when the horizontal antenna is used, and the distance should be large when the tilted antenna is used. Further, the combination of multiple frequencies and coil spacing can increase the detection depth while drilling and therefore, the adaptability to the formation resistivity of ultra-deep electromagnetic wave instrument. By reducing the operating frequency and increasing the coil spacing, the detection depth of ultra-deep electromagnetic wave instrument while drilling can reach 20−30 m. The study showed that the detection depth could bridge the gap between seismic and well logging, and make it possible to describe the oil reservoir while drilling.
Quantitative Water Injection Technology for Cavernous Fractured Karst Carbonate Reservoirs in the Tahe Oilfield
LIU Liqing, LIU Peiliang, JIANG Lin
 doi: 10.11911/syztjs.2019122
[Abstract](60) [FullText HTML](16) [PDF 574KB](1)
Abstract:
In order to resolve a series of problems such as low water injection efficiency and short longevity that faced in the development period of water injection for cavernous fractured karst carbonate reservoirs in Tahe Oilfield, a quantitative water injection technology was studied and applied on the basis of material balance equations. The theoretical basis, technical method and application effect of quantitative water injection development technology have been analyzed and expounded in three aspects, including the quantification of water injection timing, water injection parameters in single well and unit water injection parameters. The quantitative water injection technology can avoid the problems caused by qualitative water injection in the early development process, and it has been applied in 142 wells, with a cumulative EOR of 10.95×104 t, and the water injection efficiency higher than 84.3%. The results showed that the quantitative water injection technology had a great effect in the development of cavernous fractured karst carbonate reservoirs in the Tahe Oilfield, with good value of promotion and application as a best practice for similar reservoirs.
Forward Modeling in Hydraulic Fracture Detection by means of Electromagnetic Wave Logging While Drilling in Vertical Wells
XIE Yuan, LIU Dejun, LI Caifang, ZHAI Ying, SUN Yu
 doi: 10.11911/syztjs.2019133
[Abstract](235) [FullText HTML](22) [PDF 1322KB](4)
Abstract:
In order to understand the distribution of oil and gas resources in low permeability reservoirs and better control the productivity of oil wells, it is necessary to systematically study the fractures generated from hydraulic fracturing. Based on the theory of electromagnetic field, an analytical model in homogeneous and isotropic formations was established, then the formation and fracture model was established using finite element software. Forward modeling was carried out on the amplitude ratio and phase difference of induced electromotive force between the receiving coils of electromagnetic wave logging tool. The results of the forward modeling show that: signal amplitude ratio and phase difference around fracture change significantly; phase difference shows an obvious stratification, and there is higher resolution for propped fractures with different heights and different electrical conductivities of proppant. The most sensitive factor is the electrical conductivity of the proppant. A better simulation response was obtained under the source distance of the instrument was 0.25 m and the transmitting frequency was 400 KHz. The above research results indicate that it is feasible to use electromagnetic wave logging while drilling to detect hydraulic fractures in vertical wells. The research conclusions also provide a certain theoretical basis for the detection and evaluation of hydraulic fractures in vertical wells and can thus be applied in similar situations.
Key Drilling Technologies for Complex Ultra-Deep Wells in the Tarim Keshen 9 Gas Field
WANG Xuelong, HE Xuanpeng, LIU Xianfeng, CHENG Tianhui, LI Ruiliang, FU Qiang
 doi: 10.11911/syztjs.2020028
[Abstract](269) [FullText HTML](34) [PDF 672KB](11)
Abstract:
The Tarim Keshen 9 Gas Field shows the typical characteristics of ultra-deep, high temperature and high pressure environments. While drilling the Jedick formation, which is a tight sandstone reservoir, challenges such as complex geological structures, long drilling period, the coexistence of high-pressure saline and weak leakage layers in the salt-gypsum layer, difficulty in the anti-slanting and the deviations ruding rapid drilling of high steep post-salt strata are common, as well as low ROP. To overcome the problems, vertical drilling tools and optimized high-efficiency PDC bit were piloted in the post-salt strata; high-density oil-based drilling fluid, pressure management water drainage and safe drilling technologies were used in the salt-gypsum layer; 360° rotating teeth bit, turbine + impregnated bit speed-up drilling technologies were used in tight sandstone reservoirs. The combination of the above technologies constituted the key drilling technologies for complex ultra-deep wells in the Tarim Keshen 9 Gas Field. Those key technologies achieved significant field application effects. The average drilling period in the Keshen 9 Gas Field was reduced by 12.0%, the accident complex time efficiency was reduced by 4.1%, and the average ROP was increased by 13.0%. The results showed that the key technology of complex ultra-deep well drilling had high application value to increase the drilling speed and reduce the complexity in Keshen 9 Gas Field
Optimal Design of Casing Programs for Ultra-Deep Wellsin the Shunbei Oil and Gas Field
LI Shuanggui, YU Yang, FAN Yanfang, ZENG Dezhi
 doi: 10.11911/syztjs.2020002
[Abstract](325) [FullText HTML](24) [PDF 1024KB](9)
Abstract:
As exploration & development of the Shunbei Oil and Gas Field continues to deepen, the original casing program shows the problems such as high drilling risk and low efficiency, and it is necessary to optimize the casing program. With this in mind, we utilizled the logging data of drilled wells, to calculate the pore pressure, fracture pressure, and collapsing pressure of formation with Drillworks software, and the calculation results were corrected by combining with the drilling data of drilled wells and rock mechanics test results. Hence, it was possible to obtain the formation three-pressure profile of Shunbei Oil and Gas Field, and further define the necessary sealing points for geological engineering according to the profile. Based on the necessary sealing points, by comprehensively considering the drilling technical level and drilling/completion requirements, 5 types of casing program were designed. By predicting the drilling periods and drilling costs of those 5 types of casing program, and comparing the advantages and disadvantages, a four-spud unconventional casing program was selected properly. After this casing program was used in the Shunbei Oil and Gas Field, the ROP was increased by 30%–40%, the drilling period was shortened by 33–45 d, and all the wells reached the target layers smoothly. It indicated that the optimized casing program in Shunbei Oil and Gas Field improved drilling efficiency and reduced drilling risks.
Research and Application of Multi-Stage Deflective Fracturing Technology for Low Permeability Reservoir
ZHOU Dan, XIONG Xudong, HE Junbang, DONG Bo, HE Yong
 doi: 10.11911/syztjs.2019077
[Abstract](274) [FullText HTML](42) [PDF 801KB](7)
Abstract:
Problems such as small sweeping volume, short longevity and poor fracturing stimulation effects are common when conventional fracturing technology is adopted in low permeability reservoirs. In order to improve the production of low-permeability oil and gas fields, a research team developed a high-performance temporary bridging agent with high solubility, fast dissolution rate, low residue content and low damage to permeability was developed with deployment using an innovative multi-stage deflective fracturing technology. These were developed based on geological characteristics of the reservoir and the initiation mechanism of multi-stage deflective fracturing. When the formation is fractured, a temporary bridging agent is added in the frac fluid in real time to form instantaneous temporary bridging at the opening of fractures. These result in increased net pressure within fractures, and generate microfractures and branch fractures, thus forming complex network fractures and achieving the goal of volumetric stimulation. After the application of multi-stage deflective fracturing technology in Block X of the Xinjiang Oilfield, oil production dramatically increased, and daily oil production per well is 3.0 times that of wells with conventional fracturing technique. In addition, this method results in a longer stable production period, and the longevity is 66.7% higher than that with conventional fracturing. The application of multi-stage deflective fracturing technology can solve the problem of reservoir stimulation in conglomerate reservoirs and provided a new technical mean for achieving stable production in the late production period of low permeability reservoirs.
Analysis of Sensitive Factors in Dual Laterologs for Cavernous/Karst Formations near the Borehole
XIE Guanbao, LI Yongjie, WU Haiyan, LI Youyan
 doi: 10.11911/syztjs.2019134
[Abstract](314) [FullText HTML](38) [PDF 1353KB](12)
Abstract:
Igneous and carbonate reservoirs consist of formations characterized by containing extensive fractures, caverns (karst), and fractured karst. The challenges exist in the fact that there is obvious anisotropy and strong heterogeneity, resulting in huge difficulty in logging identification and quantitative evaluation. In order to provide a theoretical basis for the logging identification and evaluation of karst / cavernous formations, the numerical analysis has been used to analyze the effects of hole diameter, drilling fluid resistivity, matrix resistivity, cave size, cave fillings. Further, the distance between cave and borehole is calculated based on the response of dual laterolog using the finite element method. The results showed that the dual laterolog resistivity was significantly reduced due to the existence of near-borehole cave formation. With an increase of cave size, the reduced amplitude of dual laterolog resistivity could be increased as well. The dual laterolog resistivity is the smallest at the center of cave, and as the cave radius increases, both the deep and shallow lateral resistivity decrease. The dual laterolog resistivity increases with the increase of distance between the cave and the well wall, and the increase rate of shallow lateral resistivity is significantly faster than that of deep lateral resistivity. The research results can provide theoretical guidance for the interpretation of dual laterolog data in cavernous/karst formation..
Experimental Study on Diverted Fracturing in Carbonate Reservoir
LI Chunyue, FANG Haoqing, MOU Jianye, HUANG Yanfei, HU Wenting
 doi: 10.11911/syztjs.2020018
[Abstract](28) [FullText HTML](10) [PDF 878KB](0)
Abstract:
Shunbei carbonate reservoir has strong heterogeneity and poor connectivity. Diverted fracturing can improve complexity of fractures and enhance production. However, the behavior of diversion and propagation of the fracture has not been comprehensively understood. Therefore, it is necessary to conduct experimental study on diverted fracturing by using improved tri-axial fracturing apparatus. After injection of fracturing fluid and fracturing fluid mixed with diversion agents, by analyzing the change of treating pressure curve and surface profile of the fractures, the law of diverted fracturing and the conditions to realize diversion inside the fracture can be determined. The study shows that the complexity of fractures can be improved by temporary plugging, but in order to realize diverted fracturing by temporary plugging in fracture, nature fractures or bedding layers and the raised pressure caused by tight plugging of the agent are necessary. The law of diverted fracturing by temporary plugging in carbonate fractures provides a theoretical basis for fracturing of carbonate reservoirs in Shunbei reservoir.
Cause Analysis and Drilling Fluid Strategy for Wellbore Collapse Problem in Ultra-deep Broken Carbonate Formation of Shunbei Oil Field
CHEN Xiuping, LI Shuanggui, YU Yang, ZHOU Dan
 doi: 10.11911/syztjs.2020005
[Abstract](170) [FullText HTML](77) [PDF 1299KB](4)
Abstract:
For the wellbore collapse problem encountered in Ordovician broken limestone of Shunbei oilfield, the cause of wellbore collapse was systematically analyzed from three aspects, which were geological structure characteristics, core observation and discontinuous medium rock forces analysis. The results showed that stress concentration in strong extrusion area, formation micro fracture development and insufficient mud blocking ability, gravity effect in directional well were the three main causes of wellbore collapse. According to the causes above, the anti-collapse drilling fluid strategy was proposed, including improving the blocking capacity, controlling HPHT water loss strictly, optimizing the dynamic-plastic ratio, et al. A field test was conducted on well Shunbei X, on the base of original drilling fluid, micron and submicron rigid, plastic plugging materials were added in, and according to the particle size analysis 0.2 to 200 micron blocking particles were complete, and more than 85% were within 100 microns (70% for submicron to 46 microns). Then well Shunbei X didn’t encounter the wellbore collapse difficulty, and created the shortest period record of the reservoir section in the block. The research results can provide reference for the efficient and safe drilling in similar region.
Research and Application of Environmental-Friendly Drilling Fluid Lubricant SMLUB-E
QIAN Xiaolin, XUAN Yang, LIN Yongxue, YANG Xiaohua
 doi: 10.11911/syztjs.2019113
[Abstract](49) [FullText HTML](19) [PDF 775KB](2)
Abstract:
To overcome the shortcomings of existing lubricants, SMLUB-E was synthesized from natural fatty acids and polyols. Laboratory evaluation results show that when 1.0% SMLUB-E is added into bentonite slurry, the friction coefficient can be reduced to 0.05, and the strength of lubricating film formed is higher. Adding 2.0% SMLUB-E to polysulfonate drilling fluid can reduce the friction coefficient from 0.31 to 0.08, and the lubrication performance is better than that of 8.0% crude oil. In addition, SMLUB-E can withstand 160 ℃, and has no adverse effect on the rheological property and filtration of drilling fluid. It is easy to be biodegraded, non-toxic and environmentally friendly. SMLUB-E has been applied in deep horizontal well-TP238CH. When the content of SMLUB-E reaches 1.5%~2.0%, it shows good lubrication and friction reduction performance, greatly reduces downhole friction and avoids the complex occurrence of underpinning and sticking.
Experimental and Evaluation of Intensive Modification of Composite Electrothermal Chemical Energy Shock Wave Reservoir
LI Ang, YANG Wanyou, DING Qianshen, KANG Shaofei, YANG Wei, WU Feipeng
 doi: 10.11911/syztjs.2019129
[Abstract](59) [FullText HTML](18) [PDF 1210KB](3)
Abstract:
In order to improve the process parameter optimization and effect evaluation of the composite electrothermal chemical energy-concentrating shock wave technology, a composite electrothermal chemical energy-concentrating impact test of a large-scale concrete rock sample was first performed, and the impact rock breaking effect and control factors of the technology were evaluated; A numerical simulation model of repetitive impact under strong dynamic load can be realized, and the simulation results of large-scale rock samples are fitted and simulated. Finally, the numerical model is used to systematically evaluate the sensitivity of impact times, peaks, elastic modulus of rock, and in-situ stress to the effect of the measures. The influences of various process parameters on the number of cracks and the action distance of cracked rock caused by this technology are described, and the effect of increasing production after the measures is predicted. The test results show that the composite electrothermal chemical energy-concentrating shock wave technology can extend the shock pulse width of conventional electric pulses by 1.5 times and increase the shock amplitude by 3.0 times. After acting on the rock sample 6 times, the rock sample generates 4 macro-cracks to simulate the wellbore Fragmentation of varying degrees. The results of the study clarify the scope of process parameters and further evaluate the effect of the measures, providing theoretical guidance for the use of composite electrothermal chemical energy-concentrating shock wave technology to improve the effect of reservoir enhancement.
Bridge concentric seal measurement and adjustment integration technology in Changqing Oilfield
YANG Lingzhi, LIU Yanqing, HU Gaixing, SHEN Xiaoli, BI Fuwei
 doi: 10.11911/syztjs.2020023
[Abstract](76) [FullText HTML](15) [PDF 746KB](3)
Abstract:
In order to improve the testing efficiency of small water separate injection technology for directional Wells in Changqing oilfield, and reduce the operating intensity and testing cost, the integrated layered water injection technology and key tools for concentric inspection, sealing, measurement and regulation were developed. The technology uses the electromechanical integration control technology, ground control system through the cable control down hole testing instrument which can adjust the inspection seal and test work, mechanical clutch structure technology principle, the existing electric direct reading test sealing apparatus with concentric electric tuning meter integrated test seal the integration measurement instruments, have the early test instrument, measuring instrument function, further enhance integration, degree of automation. This technology has been applied to over 430 wells in Changqing oilfield, which has met the requirement of completing all procedures of well seal inspection and test adjustment in one operation. The success rate of test and adjustment is 98%, the single-well test and seal test time is reduced from 6–8 h to 4 h, the annual operating cost of single well is reduced by RMB 9,600. The successful development of the integrated layered water injection technology with concentric inspection, sealing, measurement and adjustment provides a new and efficient testing tool for the low-cost development of low permeability reservoirs.
Drilling Technology of Horizontal Well in Long Horizontal Section of Shale Oil in Longdong Area of Changqing Oilfield
Liu weirong, Ni huafeng, Wang xuefeng, Shi zhongyuan, Tan xuebin,    
 doi: 10.11911/syztjs.2020029
[Abstract](63) [FullText HTML](25) [PDF 714KB](4)
Abstract:
In recent years, horizontal Wells of chang 7 shale have been developed by volume fracturing in longdong area of changqing oilfield. In order to better improve reservoir contact area and fracturing effect, In 2019, changqing oilfield deployed 20 long horizontal Wells in block 233, west of maling. The drilling practice shows that it is difficult to control the trajectory of the second large hole, the mechanical drilling speed of the long horizontal section is low, it is difficult to stop the leakage in the horizontal section, the wellbore is easy to lose stability, and the completion casing is facing challenges. Aiming at the technical problems, through optimizing the well trajectory, optimizing the personalized drill bit, optimizing the drill assembly, strengthening the drilling parameters, using the new plugging material, casing floating down and other technologies, the full length horizontal well was successfully completed, the first drilling of h50-7, an ultra-long horizontal horizontal well with a length of 4 088 meters, was completed. Combined with the h50-7 well of hua, this paper introduces the application of the above technologies, and verifies the effectiveness of these technologies with an example, which provides reference experience for drilling ultra-long horizontal Wells in China.
Analysis and Correction of Influencing Factors of the Spectral Azimuthal Gamma Ray Logging While Drilling
ZHENG Jian, GAO Hui, HUANG Lugang, DUAN Junya, DONG Duo
 doi: 10.11911/syztjs.2019131
[Abstract](372) [FullText HTML](65) [PDF 2438KB](7)
Abstract:
There are some differences in the LWD spectral azimuthal gamma ray tool (SAGR) under different wellbore and formation conditions, which will affect subsequent logging interpretation and geological guidance. Therefore, it is necessary to study the influence of various wellbore and formation factors on the gamma spectroscopy while drilling, and correct the influence of non-formation factors. Firstly, the SAGR instrument structure is compared. Based on this, the instrument structure to be used is determined and the corresponding MCNP model is established. Then, the response of SAGR under different wellbore and formation conditions is simulated based on Monte Carlo method. The effects of mud density, KCl, formation matrix and the inclination, azimuth and thickness of inclined radioactive formation on the LWD SAGR Tool are simulated, and the correction process of the influence of well factors is given. The results show that the total count rate is positively correlated with KCl, dip angle and thickness of inclined radioactive formation, and negatively correlated with mud density, formation matrix density and azimuth of inclined radioactive formation. KCl can change the shape of energy spectrum, while other factors do not change the shape of energy spectrum. The shale content and K、U、Th content calculated by the count rate or energy spectrum corrected by the wellbore influence factors are closer to the true value, which provides more accurate guidance for logging interpretation and geosteering.
Research Status and Prospects of Intelligent Drilling
LI Gensheng, SONG Xianzhi, TIAN Shouceng
 doi: 10.11911/syztjs.2020001
[Abstract](280) [FullText HTML](44) [PDF 922KB](18)
Abstract:
As the petroleum industry gradually turns its attention to the novel and hard-to-recovery resources including unconventional, low-permeability, ultra-deep, and subsea oil and gas, there appears a series of new problems and challenges in drilling engineering in terms of safety, economy, and efficiency. The intelligent drilling technology has become a hotspot for domestic and foreign researchers. Based on the sophisticated technologies such as big data and artificial intelligence, the intelligent drilling technology is hoped to realize the advanced detection, intelligent steering, closed-loop control and intelligent decision-making during the drilling processes. In this way, it can lead to dramatic increases of production and recovery, and at the same time reduce the cost. This paper is focused on the history and state of art of the key intelligent drilling technology around the world, including the intelligent optimization of well trajectory and rate of penetration, intelligent steerable drilling, downhole closed-loop regulation and control, intelligent monitoring and decision-making. Furthermore, the current status of intelligent equipment, which includes the intelligent drilling rig, intelligent drill pipe, intelligent bit, intelligent managed pressure drilling system, intelligent steerable drilling system, are analyzed. It is pointed out that there is a need to strengthen the cross-border integration of drilling engineering, frontier theory and technology, and promote collaborative innovation and establish a sound intelligent drilling technology system based on the rapid development of artificial intelligence in China, which further provides technical support for the efficient exploration and development of complex hydrocarbon reservoir and development strategies of oil and gas resources in China.
Gas-Water Composite Flooding Technology for Fractured and Vuggy Carbonate Reservoirs in Tahe Oilfield
ZHANG Wei, HAI Gang, ZHANG Ying
 doi: 10.11911/syztjs.2019124
[Abstract](338) [FullText HTML](139) [PDF 950KB](16)
Abstract:
After water flooding, a large amount of “attic oil” will be left in the structural top of fractured and vuggy carbonate reservoirs in the Tahe Oilfield. Due to weak lateral drives, a large amount of remaining oil will be accumulated between wells even with nitrogen flooding. According to the reservoir characteristics and remaining oil distribution features of such reservoirs, a gas-water composite flooding technology was studied. Based on the analysis of gas-water composite flooding mechanisms, different gas-water composite flooding development modes have been established according to the distribution features of remaining oil. Based on the characteristics of inter-well communication pathways, the development well pattern was designed taking into consideration the unique conditions, and gas-water composite flooding parameters were designed from historical water flooding data and the cumulative gas injection volume. The gas-water composite flooding technology was applied in 7 injection-production well group of Block 4 of the Tahe Oilfield, and the oil production of this well group was increased by 80.0 tons on average. The results indicate that gas flooding in the gas-water composite flooding drives the “attic oil” to the water flooding channel first, and then the water flooding provides lateral driving force to transport it out.
Ultra-High Molecular Weight Polymer Flooding Technology for Heavy Oil Reservoirs in Block B125 of the Gucheng Oilfield
TAO Guanghui, SHU Huadong, LIU Bin
 doi: 10.11911/syztjs.2019127
[Abstract](302) [FullText HTML](135) [PDF 951KB](20)
Abstract:
Common heavy oil reservoir in Block B125 of the Gucheng Oilfield shows strong heterogeneity, and the average crude oil viscosity is above 1 000 mPa·s, which makes it more difficult to further improve oil recovery rate. Technical advantages of ultra-high molecular weight polymer in enhancing the recovery factor of common heavy oil were evaluated through viscosity, rheology and oil displacement tests. The effect of sulfur-containing sewage on the performance of polymer solution was investigated. The tests show that ultra-high molecular weight polymer has a superior viscosity increasing property, and the viscosity is more than 40% higher than that of conventional polymers at the same mass concentration, and its recovery factor is 3.4 percentage points higher than that of the conventional polymers with the same viscosity. Sulphur-containing sewage will reduce the viscosity of polymer solution over 10%, the recovery factor can be decreased by 3.0 percentage points, and elasticity will be significantly weakened. A total of 22 polymer injection wells were deployed in Block B125. By the end of 2018, a total of 0.22 PV of polymer solution was injected, and the injection pressure increased 3.5 MPa. The daily oil production rate increment was 45.0 tons and the cumulative oil production increment reached 1.84×104 t, while water cut was decreased by 9.0 percentage points and EOR was increased by 1.19 percentage points in this stage. The research demonstrates that the ultra-high molecular weight polymer flooding technology can bring a largely increased EOR of high viscosity common heavy oil reservoirs, and it can provide a new technical route and on-site basis for enhancing oil recovery in this type of reservoirs.
Wellbore Arrangement Schemes for Fishbone Wells in the Sadi Reservoir of the H Oilfield in Iraq
NIE Zhen, YU Fan, HUANG Genlu, LI Wei, LIANG Qimin
 doi: 10.11911/syztjs.2019120
[Abstract](431) [FullText HTML](182) [PDF 967KB](6)
Abstract:
In order to effectively develop the Sadi ultra-low permeability reservoir, the optimal method for arranging fishbone well schemes was studied in accordance with the characteristics of reservoir and the conditions of fishbone well drilling, by comprehensively considering the reservoir geology and engineering factors. as the goal was to obtain the optimal fishbone well arrangement scheme that can satisfy the need for both development and smooth drilling under extreme drilling conditions. First, the ultimate drilling depths of the main wellbore and branch hole of the fishbone well were determined based on the geological conditions of the Sadi reservoir and the drilling capacity of conventional directional wells. Then, by taking the cumulative oil production as the preferred target, the influences of main parameters (such as the number of branch hole, the length of branch wellbore, the spacing between adjacent branch holes, the included angle between the branch hole and main wellbore, and different fishbone wellbore deployment schemes) on the cumulative oil production were analyzed to determine the wellbore deployment scheme with higher cumulative oil production. Next, according to the drilling difficulty of different trajectories of the fishbone well, a corresponding model was established to evaluate the drilling risks of different wellbore deployment schemes and determine the scheme with lower drilling cost. Finally, the wellbore arrangement schemes for 4 branch hole length of 730. 00 m and 3 branch hole length of 800.00 m were selected as the best schemes for the fishbone well of the Sadi reservoir. The application of the optimal wellbore arrangement scheme has provided high cumulative oil production, with controllable drilling risk and lower drilling cost. The proposed optimal method of fishbone well arrangement schemes combined closely the drilling engineering and the reservoir engineering geology, so as to provide the reservoir engineer an idea of selecting a fishbone well arrangement scheme, and to give a reference for design of fishbone wellbore for similar oilfields.
High-Efficiency and Safe Drilling Technologies for Development Wells in the Beibuwan Basin
LIU Xianyu, GUAN Shen, HAN Cheng, CHEN Li, CAO Feng
 doi: 10.11911/syztjs.2019116
[Abstract](331) [FullText HTML](158) [PDF 690KB](19)
Abstract:
The Beibuwan Basin in the western South China Sea has well developed micro-fractures and strong water sensitivity, which leads to frequent drilling complexities, especially wellbore instability in the second member of the Weizhou Formation. In order to improve the drilling efficiency of development wells in Beibuwan Basin, drilling technologies and practices were summarized. The wellhead was constructed by sidetracking the riser of the abandoned wellhead slot, so as to make full use of the wellhead slot; the seawater polymer drilling fluid system was used to drill the surface casing section while reducing the borehole size of surface casing section, and to achieve deep drilling of this section; the strong plugging full oil-based drilling fluid was used to penetrate the target layer which named Weizhou 2 Formation ; the casing program was optimized, and the intermediate casing and production casing were integrated, so as to improve the drilling safety of the target layer and reduce the operation time. Thus, high-efficiency and safe drilling technologies for development wells in Beibuwan Basin were finally formed. With these technologies applied in more than 30 wells in several oilfields in Beibuwan Basin, the waste of wellhead slot resources was avoided, the drilling fluid cost for surface casing section was reduced, the complex accident ratio of the target layer was reduced, the ROP of the whole well was improved by more than 20%, and the drilling period of development well was shortened by nearly 25%. These drilling technologies could provide technical references for the efficient development of similar oilfields.
Temperature Distribution of Heavy Oil Reservoirs under High Frequency Electromagnetic Heating and an Analysis of Its Influencing Factors
WANG Zhengxu, GAO Deli
 doi: 10.11911/syztjs.2019128
[Abstract](788) [FullText HTML](454) [PDF 4566KB](33)
Abstract:
In order to accurately analyze the factors affecting the temperature distribution of heavy oil reservoirs during high frequency electromagnetic heating, a mathematical model with dynamically varied reservoir properties was established based on the theories of electromagnetic field and heat transfer. In this model, frequency dependence of electrical conductivity and the relative permittivity of heavy oil reservoirs were taken into consideration, along with the temperature dependence of thermal conductivity and specific heat. In addition, COMSOL software of was employed to develop a mathematical model. Finally, the influencing laws governing temperature variation factors were studied by a contrast method. The calculations reflect a direct correlation between electromagnetic wave power and reservoir heating depth, and they demonstrate that the increase of electromagnetic wave power helps to increase the heating depth of reservoir. Although large electromagnetic wave frequency can lead to high temperature area nearby the wave source, the temperature value decreases sharply with the increase of depth. The results of a temperature calculation considering the dynamic change of reservoir properties differ from those calculated based on the constant reservoir properties. Reservoir temperature increases with the relative permittivity and conductivity within a certain range of variation. The results show that reservoir properties, electromagnetic wave power and frequency have a significant impact on temperature distribution of the reservoir and perhaps are prime influencers. The mathematical model that takes into consideration the dynamic change of reservoir properties provides a theoretical basis for the field application of a high frequency electromagnetic heavy oil heating technology.
The Optimization of Rubber Sealing Materials for Key Equipment in Polar Drilling
CHEN Yuanpeng, WANG Zhiyuan, SUN Baojiang, CHEN Ye, ZHENG Kaibo
 doi: 10.11911/syztjs.2019111
[Abstract](550) [FullText HTML](229) [PDF 1154KB](20)
Abstract:
The unique low temperature environment of polar drilling hardens rubber gradually to the point of even vitrifying it so it loses its original elasticity. This can easily cause the sealing failure of key drilling equipment, such as mud pump and BOP, which affects normal production and brings about potential safety risks. Therefore, it is necessary to optimize the rubber sealing materials used in the key equipment for polar drilling. According to the National Standards GB/T 528—2009 and GB/T 7759.2—2014, the rubber materials were subjected to uniaxial tension and compression permanent deformation tests at the temperature of 20 ~ –50 °C, and the test data and the hyper-elastic constitutive models of several common rubbers were fitted to obtain the model parameters, so as to analyze the applicability of these constitutive models under low temperature conditions. The sealing performance of rubber O-ring at –45 °C was simulated and analyzed by using ABAQUS finite element software, and found the location of the seal failure which is easy to occur at low temperature. According to the analysis, Polynomial (N=2) model and Ogden (N=3) model can accurately describe the mechanical properties of rubber under low temperature and small deformation conditions. Silicone rubber, gas rubber and nitrile rubber can still maintain superior sealing performance under polar environments (–45 °C), so they can be used as the rubber sealing materials for key equipment of polar drilling. The analysis of rubber super-elastic constitutive model at low temperature and the optimization of rubber sealing materials can provide theoretical guidance and support for the future polar drilling of China.
Analyzing and Understanding the Influencing Factors of CO2 Flooding in the Subei Complex Fault Block Reservoirs
TANG Renxuan, LIANG Po, WU Gongyi, CHEN Ju, LIANG Cui
 doi: 10.11911/syztjs.2019125
[Abstract](417) [FullText HTML](309) [PDF 881KB](17)
Abstract:
The performance of CO2 flooding in the complex fault block reservoirs of the Subei Basin varies greatly. In order to find effective measures to improve the development of these unique fault-block reservoirs, the main influencing factors were analyzed. Based on the data from 9 CO2 flooding blocks in north Jiangsu, the influences of well type, fracturing conditions, initial production before gas injection, the injection-production ratio and the gas injection method on CO2 flooding effects were analyzed. The analysis results show that the development effect of vertical wells is better than that of horizontal wells, and it is better for non-fractured wells than fractured. The higher the initial production of the well, the better the CO2 flooding effect. The optimal injection-production ratio is around 2.5, while CO2 injection methods play an insignificant role in the development effect. The results show that those factors, such as low permeability reservoir well type and the necessity of reservoir stimulation, are the main factors influencing CO2 flooding. Those issues need to be fully considered in improving the CO2 flooding effect in the complex fault block reservoirs in the Subei Basin.
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The Current Status and Development Recommendations for Dry Hot Rock Fracturing Technologies at Home and Abroad
CHEN Zuo, XU Guoqing, JIANG Manqi
2019, 47(6): 1-8.   doi: 10.11911/syztjs.2019110
[Abstract](489) [FullText HTML](237) [PDF 3809KB](33)
Abstract:
Dry hot rock is a special geothermal resource featuring large reserves, wide distribution, clean energy generation, and recyclability. The United States, France and other countries have successfully developed and utilized dry hot rock to generate electricity and heat. Abundant dry hot rock resources have been developed in southern Tibet, western Yunnan, and the coastal areas of the southeast China, but they have not yet been exploited effectively. The efficient development of dry hot rock is of great significance in adjusting energy structure, reducing environment pollution, and coping with climate change challenges. Proper hydraulic fracturing can generate a complex fracture system in thermal reservoirs that will enhance heat exchange volume, which is the key element in the transformation from dry hot rock resources into energy. Based on the research status of dry hot rock fracturing technologies worldwide, this paper analyzed the characteristics of foreign main dry hot rock fracturing technology, and pointed out the situation and difficulties of fracturing faced in the development of dry hot rock in China. It is recommended in this paper that research focus on high temperature dry hot rock mechanics and in-situ stress characteristics, rupture and extension mechanisms of frac under thermal stress, ultra-high temperature staged/zonal fracturing tools, volume fracturing design method for high temperature hard formation and software development, and long-term real-time monitoring of fractures so as to develop the matched fracturing technology as soon as possible. At that point it can then promote the development and utilization of dry hot rock resources.
Key Technologies for Deep Marine Shale Gas Drilling in Southern Sichuan
LIU Wei, HE Long, HU Daliang, LI Wensheng, JIAO Shaoqing
2019, 47(6): 9-14.   doi: 10.11911/syztjs.2019118
[Abstract](549) [FullText HTML](305) [PDF 733KB](51)
Abstract:
Deep marine shale gas in the southern Sichuan Basin has a deep burial depth, high formation temperature and formation pressure, poor rock drillability and thin high-quality reservoirs. Further, the contradictions between fast drilling and borehole quality, shale collapse and drilling cost, time-controlled drilling and the variable probability of encountering high-quality reservoirs have hindered its effective development. To this end, based on the experience of conventional shale gas development, through the differentiated casing program and borehole trajectory design, by adopting bent-housing mud motor BHA, optimization of drilling parameters, conducting vertical drilling and gas drilling technical tests, development of high-performance water-based drilling fluid and the borehole trajectory control, a set of key drilling technologies suitable for the effective development of deep shale gas in the Southern Sichuan were formed. Those technologies were applied in 27 deep marine shale gas wells in the Southern Sichuan, resulting in the fact that the the drilling cycle was shortened by 46.0% and the rate of high-quality encountering economic reservoirs reached 93.17%. The results indicated that those key drilling technologies could sustain the effective development of deep marine shale gas in southern Sichuan, and they could provide references for the development of similar shale gas reservoirs at home and abroad.
Plugging Technology for HTHP Wells in the Yingqiong Basin of the South China Sea
HAN Cheng, HUANG Kaiwen, LUO Ming, LIU Xianyu, DEND Wenbiao
2019, 47(6): 15-20.   doi: 10.11911/syztjs.2019081
[Abstract](511) [FullText HTML](244) [PDF 968KB](52)
Abstract:
The Yingqiong Basin in western South China Sea is characterized by complex geological conditions, high bottomhole temperatures and pressures, and lost circulation which occurs frequently during drilling into the target layer. In order to solve the problem of frequent lost circulation in target layer, the main causes of lost circulation were analyzed, the idea of combining the high temperature resistant rigid plugging materials with high temperature resistant elastic plugging materials was followed, and a plugging slurry was prepared by adding DXD (a high temperature resistant rigid plugging material) and TXD (a high temperature resistant elastic graphite plugging material) into drilling fluid. The performance evaluation showed that the density of plugging slurry could reach 2.40 kg/L and the temperature resistance could reach 200 °C. The DXD could form bridges in the induced fractures, while the TXD could enter the residual pores of induced fractures under pressure difference, preventing the induced fractures from further opening and expanding, blocking the induced fractures and improving the pressure-bearing capacity of formation. This plugging slurry had been applied in several high temperature and high pressure (HTHP) wells in the Yingqiong Basin with the success rate of plugging increasing from 30% to 80%, indicating that the plugging slurry could block the induced fractures in the target layer of the Yingqiong Basin, improve the pressure-bearing capacity of formation and the success rate of plugging, and solve the problem of frequent lost circulation in the target layer.
Completion Technologies for HTHP Gas Fields in the Yinggehai Basin
HUANG Liang, WEI Anchao, WANG Erjun, XU Jing, ZHANG Chao, FENG Xuesong
2019, 47(6): 21-26.   doi: 10.11911/syztjs.2019098
[Abstract](332) [FullText HTML](137) [PDF 869KB](16)
Abstract:
The F Gas Field in Yinggehai Basin of the South China Sea is an HTHP gas field, characteristics of high temperature, high pressure and high CO2 content has been the challenge to the integrity of wellbore, so the completion method was selected pertinently according to the characteristics of reservoirs. Based on the principle of keeping both the safety and the economy, the tubing/casing has been made by modified 13Cr material, and designed the different types of production strings. In terms of the characteristics of gas field and the development requirements, the selection of wellhead Christmas trees and downhole tools was carried out properly, the perforation pipe string was designed, and the proper annulus protection fluid was developed. In the end, it formed a completion technology suitable for the development of HTHP offshore gas fields with high acidic gas content. This completion technology has been applied in more than 10 wells of this gas field, and no sustained annulus pressure was observed during the production process, which indicated that the developed completion technology could effectively ensure the wellbore integrity of such gas fields, and provide supports for the large-scale development of HTHP gas fields in the Yinggehai Basin.
Influence of the Rotary Speeds of the Internal and External Rings of Pointed Rotary Steering System on the Rock-Breaking Efficiency of PDC Bit
ZHANG Guangwei, GAO Situ, QIAO Yang, TIAN Fan
2019, 47(6): 27-33.   doi: 10.11911/syztjs.2019096
[Abstract](598) [FullText HTML](341) [PDF 1424KB](38)
Abstract:
The goal was to improve the rock-breaking efficiency of the pointed rotary steering drilling system. To do so, a new process was developed, based on the research of bit kinematics, the digital PDC bit model and the digital rock model. The team used Matlab software, which, combined with the discretization processing of rock model, was able to simulate the interaction between PDC bit and rock under the condition of rotary steering drilling, and further obtain the quantitative calculation method of rock-breaking efficiency. The influence of the rotary speeds of the internal and external rings of pointed rotary steering system on rock-breaking efficiency of PDC bit was analyzed, and the rock-breaking law at different time steps was obtained. The results showed that for the rock with a shear strength of 11 MPa, an internal friction angle of 22º and a friction coefficient of 0.2, it had an optimal rock-breaking speed ratio of about 1.0, and the pointed rotary steering system presented a steady state cutting during the drilling process. Its rock-breaking efficiency was closely related to the speed ratio of the inner and outer eccentric rings. As the speed ratio increased, the rock-breaking efficiency also increased, but it eventually stabilized. The research results demonstrated a possible theoretical guidance for improving the drilling efficiency of pointed rotary steering system.
Research on Renewable Biosynthetic-Based Drilling Fluid Systems
XIE Yuning
2019, 47(6): 34-39.   doi: 10.11911/syztjs.2019097
[Abstract](594) [FullText HTML](310) [PDF 656KB](33)
Abstract:
Oil-based drilling fluids generally have various disadvantages, for example, the base oil is difficult to degrade and non-renewable. Therefore, an investigation on the renewable biosynthesis oil-based drilling fluid system was carried out. The biosynthetic base oils were synthesized by the catalytic hydrogenation and molecular isomerization of natural bio-oils and fats. Based on the biosynthetic base oil and modified organic soil, the renewable biosynthesis-based drilling fluid system was formed through adding other drilling fluid additives and the optimized dosage, and its performance was evaluated. The biosynthetic base oil was a mixture of C12–C24 branched isoparaffins, which had excellent safety, environmental protection and viscosity-temperature properties. The high temperature and high pressure filtration loss of the renewable biosynthesis-based drilling fluid system was lower than 12 mL, the sedimentation stability was good, the demulsification voltage was up to 768 V, and the 96 h semi-lethal concentration was greater than 1 000 000 mg/L. The biosynthetic oil was able to resist the invasion of 20% formation water and 10% inferior soil, and the rolling recovery rate of cuttings reached 98.06%; the permeability recovery rate of the contaminated cores was up to 83.5%–92.3%. The research results showed that the oil with a biosynthetic base possessed the advantages of low toxicity, environmental protection, degradability and regenerability. The prepared drilling fluid exhibited good properties in emulsion stability, anti-pollution, lubrication, inhibition, reservoir protection, safety and environmental protection, which fully met the needs of drilling fluids under complex geological conditions.
Anti-Sloughing Drilling Fluid Technology for the Paleogene Shale Stratum of the Xijiang Oilfield in the South China Sea
ZHANG Weiguo, DI Mingli, LU Yunhu, ZHANG Jian, DU Xuan
2019, 47(6): 40-47.   doi: 10.11911/syztjs.2019103
[Abstract](766) [FullText HTML](339) [PDF 1557KB](32)
Abstract:
In order to address the problems of borehole caving, blockage and sticking while drilling the Paleogene shale formation in the Xijiang Oilfield of the South China Sea, technical research has been carried out on anti-sloughing drilling fluids. Through analyses of stratigraphic mineral composition, physicochemical properties and mechanical parameters, the mechanisms of wellbore instability in the Paleogene shale formation have been clarified, and have established the relationship chart between the drilling fluid density required for maintaining wellbore stability and rock cohesion, so as to determine the minimum rock cohesion index required to sustain wellbore stability. In order to improve the strength of surrounding shale immersed in drilling fluid, a new anti-sloughing drilling fluid formula was obtained through selection of proper inhibitor and plugging agent as well as their optimal dosages. The research showed that the intrusion of drilling fluid filtrate would lead to the reduction of shale strength, which is the main reason for the wellbore instability of Paleogene shale formation in this oilfield; After immersing for 10 days in the new anti-sloughing drilling fluid added by 2.0% polyammonium salt, 0.5% nano-silica and 3.0% calcium carbonate into KCl-polymer drilling fluid, the rock sample still has the cohesive force of 8.8 MPa, which satisfies the required rock cohesion of greater than 8.7 MPa in the expected period. According to the comprehensive analysis, the new anti-sloughing drilling fluid featured by good inhibition, plugging and anti-sloughing effect, it can solve the problems encountered during Paleogene shale drilling in the Xijiang Oilfield of the South China Sea, and effectively control the borehole enlargement rate.
Low-Activity Drilling Fluid Technology for the MaHW1602 Horizontal Well in the Mahu Oilfield
ZHENG Chengsheng, LAN Qiang, ZHANG Jinghui, LI Gongrang
2019, 47(6): 48-53.   doi: 10.11911/syztjs.2019115
[Abstract](465) [FullText HTML](282) [PDF 658KB](14)
Abstract:
Well MaHW1602 in Mahu Oilfield owns complex formation conditions, the target layer in the Triassic Baikouquan Formation contains hard mudstone and loose conglomerate, and downhole events such as collapse and caving are prone to occur during horizontal section drilling. Due to the insufficient collapse resistance of the " desulfurization” drilling fluid applied in this area in recent years, through analyzing the formation characteristics and the challenges in drilling fluids, the activity modifier, plugging agent and inhibitor were preferably selected in the laboratory, and the non-sulfonated low-activity drilling fluid system was further developed. The results of indoor test show that the plugging rate of low-activity drilling fluid exceeds 90%, and the average water activity is 0.863, which meets the requirements of field drilling. The drilling fluid was applied in the third spud section of Well MaHW1602, there was no obvious hole enlargement in the loose and collapsing-prone section, the wellbore was regular, and the average hole enlargement rate was 6.5%. In addition, there was no obvious weight stacking during drilling, the electrical logging and casing RIH were performed smoothly without any problems such as the rapid changes in drilling fluid properties, lost circulation during RIH or pump starting, etc. Research and field application suggest that the low-activity drilling fluid has good plugging and anti-sloughing properties, which can meet the requirements for safe drilling of long lateral horizontal wells in the Mahu Oilfield.
The Prediction of Wellbore Temperature and the Determination of Thief Zone Position under Conditions of Lost Circulation
WU Xueting, ZOU Yun, LU Yanying, ZHAO Zengyi, ZHOU Chenghan
2019, 47(6): 54-59.   doi: 10.11911/syztjs.2019119
[Abstract](534) [FullText HTML](249) [PDF 863KB](27)
Abstract:
In view of the fact of low accuracy of wellbore fluid temperature prediction and difficulty in identifying the position of the thief zone when the circulation loss occurs, a model of wellbore temperature field under lost circulation was established based on the analysis of wellbore heat transfer laws by comprehensively considering the influences of heat source items and variable mass flow on wellbore temperature. The reliability of this model was verified by field measured data, and the influences of the leakage rate and the thief zone on the temperature distribution laws of wellbore were analyzed. The numerical simulation results show that when compared with the model from Chen, the outputs from the new model are closer to the measured temperature, with the average relative error of 2.1%. The leakage rate imposes much greater influence on the bottom hole fluid temperature than the wellhead fluid temperature. In addition, when the leakage occurs in the upper open hole section, there is an inflection point on the temperature gradient distribution curve of the annulus fluids, and the position of the point is consistent with that of thief zone. The research results suggest that the model can accurately predict wellbore temperature distribution under lost circulation conditions, and the position of the thief zone can be determined in the field according to the annulus temperature gradient distribution curve.
Slim Liner Cementing Technology for Ultra-Deep Wells with a Narrow Annulus in No.1 District of Shunbei Block
ZOU Shuqiang, ZHANG Hongwei, Eerqm, LI Xiang
2019, 47(6): 60-66.   doi: 10.11911/syztjs.2019114
[Abstract](399) [FullText HTML](165) [PDF 1041KB](14)
Abstract:
Slim liner cementing in ultra-deep wells with narrow annulus in the No.1 District of the Shunbei Block faces a series of technical challenges such as weak cement sheath, high displacement pumping pressure, low displacement efficiency, high bottomhole temperature and the development of high-pressure brine layer, which compromises the cementing quality. In order to solve those problems, on the basis of summarizing the previous operation experiences, small liner cementing technology for ultra-deep wells with narrow annulus in the No. 1 District of the Shunbei Block was formed by improving wellbore preparation technologies, optimizing the high temperature/gas channeling-proof elastic toughness cement slurry system, conducting cement stone sealing integrity research and carrying out cementing rheology design and stable-killing gas channeling-proof optimization. It has been applied in 3 wells in this area with good cementing quality. The subsequent operations were free from water intrusion, ensuring the long-term sealing of section with a narrow annulus. This cementing technology can not only effectively solve the cementing problems of this block, but also effectively ensure the safe and efficient development of the block.
A Logging Data-Based Calculation Method for the Horizontal TIV Formation In-Situ Stress
XIA Hongquan, LIU Chang, LI Gaoren, JIANG Tingwei
2019, 47(6): 67-72.   doi: 10.11911/syztjs.2019130
[Abstract](399) [FullText HTML](184) [PDF 1222KB](19)
Abstract:
Given the TIV anisotropy characteristics of low porosity/permeability formations, the accurate calculation of horizontal in-situ stress is essential for the perforation and fracturing designs of those reservoirs. In order to more accurately and effectively calculate the horizontal in-situ stress of a TIV formation, considering the low-pressure characteristics of such formation, the Bowers method was used to obtain the formation pore pressure. Then, the array acoustic logging data was used to obtain the anisotropic rock mechanical parameters (the vertical/ horizontal Young’s modulus of elasticity and Poisson's ratio) of TIV formation. Considering the influence of bedding plane occurrence on horizontal in-situ stress, the traditional Sn model was improved and a new calculation model for the horizontal in-situ stress of TIV formation was established. The horizontal in-situ stresses of the TIV formations in the Chang 6, Chang 7 and Chang 8 sections of the Heshui area of the Ordos Basin were calculated by this new model. The maximum relative errors between the calculated and the measured maximum/minimum horizontal in-situ stresses were 8.70% and 7.86%, respectively, which were smaller than those of in-situ stresses calculated by Sn model. The results showed that the horizontal in-situ stress calculated by this new model was more in line with the variation laws of the vertical and horizontal distributions of the actual in-situ stress, which could provide a more reliable reference for the hydraulic fracturing design of tight oil reservoirs.
An Evaluation of the Stimulation Effect of Horizontal Well Volumetric Fracturing in Tight Reservoirs with Complex Fracture Networks
LI Xianwen, LIU Shun, CHEN Qiang, SU Yuliang, SHENG Guanglong
2019, 47(6): 73-82.   doi: 10.11911/syztjs.2019126
[Abstract](533) [FullText HTML](299) [PDF 2095KB](19)
Abstract:
Improvements on the effect of fracturing stimulation is essential for the economic and effective development of tight reservoirs, and it is necessary to consider the distribution characteristics of complex fracture networks while evaluating the effect of fracturing stimulation. Based on microseismic data, distribution characteristics of secondary fractures were obtained by using a fractal random fracture networks generation algorithm. By considering the physical properties variation of the near borehole region of fractured horizontal wells, a mathematical model of fluid flow in multi-zone porous media of fractured horizontal wells was established and then resolved. Based on the model, the influences of the complexity of secondary fractures on the flow were studied. The results demonstrate that the complexity of secondary fractures has a significant impact on the entire flow stage. The findings include the larger the fractal dimension, the higher the yield; the wider the stimulated zone, the longer the steady-state turbulence early linear flow and the bilinear flow will last. The fracturing stimulated area with the distributed secondary fractures is the main area in the early to middle stage of production, and it makes the largest contribution to the production. Thus, during actual production, the best approach is to increase the stimulated volume so as to improve the early production and to maximize the EOR of reservoirs. The research results can provide a theoretical basis ofr the evaluation of a volume fracturing effect of tight reservoirs and the optimization of fracturing design.
Design and Experimental Study of an RFID Intelligent Sliding Sleeve
LI Wei, XIA Yang, CHEN Xi
2019, 47(6): 83-88.   doi: 10.11911/syztjs.2019123
[Abstract](376) [FullText HTML](172) [PDF 933KB](23)
Abstract:
In order to overcome the deficiencies of conventional horizontal well staged fracturing technologies, including complicated operations, the inability to achieve full drift size and limited number of fracturing stages, a horizontal well staged fracturing technology with an RFID intelligent sliding sleeve was proposed. The pipe string structure and technical challenges of RFID intelligent sliding sleeve fracturing technology were studied, on the basis of analyzing the characteristics of horizontal staged fracturing technologies and experiments carried out scheme optimization, simulation analysis, unit test and indoor prototype test for an RFID intelligent sliding sleeve structure. The test results showed that the RFID intelligent sliding sleeve could be smoothly opened to the preset openness under the temperature of 120 °C and pressure difference of 0–70 MPa. The RFID tag ball can control the window of RFID intelligent sliding to the preset openness, with RFID communication having an excellent success rate. The reesults indicated that RFID intelligent sliding sleeve-based horizontal well staged fracturing technology could reduce the cost of horizontal well fracturing, improve the efficiency of oil and gas development, and provide technical support for the intelligent, cost-saving and efficient development of oil and gas, with good foundation for future application.
The Research and Application of a Key Tool for Coiled Tubing Fishing with Coiled Tubing
AIBAIBU Abulimit, PANG Dexin, WANG Yiquan, GUO Xinwei, YANG Wenxin, JIAO Wenfu
2019, 47(6): 89-95.   doi: 10.11911/syztjs.2019117
[Abstract](530) [FullText HTML](277) [PDF 1462KB](33)
Abstract:
In view of the low efficiency, high risk and high labor intensity of coiled tubing fishing with a conventional tubing string, research was conducted to investigate the current status of coiled tubing operation technologies. The process of coiled tubing fishing with coiled tubing was proposed, and a specific tool was developed. By virtue of its modular design, the tool was able to integrate the functions of fish top rotation entrance, fish top detection, fish top capture and shearing into the tool, so that the tool could adapt to the operation conditions of coiled tubing fishing. The results of simulation calculation and laboratory test verified that the performance of this tool met the desired design requirements. This fishing tool was used in Well X–1 of Tarim Oilfield on coiled tubing, and it finished 13 fishing jobs in ϕ88.9 mm production string. In total 2 851.87 m of ϕ38.1 mm coiled tubing that had been seriously stuck in the hole was retrieved, and the retrieval rate was up to 100%, while the fishing efficiency was four times higher than that of the conventional fishing string. The field application also verified the stability of tool’s performance. Studies suggested that this coiled tubing fishing tool could also be effectively applied in coiled tubing fishing, and it could provide technical references in the future for fishing in coiled tubing.
Solution of Nonlinear Seepage Model for Fracture Well Groupin Low Permeability Reservoirs
HUANG Yingsong
2019, 47(6): 96-102.   doi: 10.11911/syztjs.2019078
[Abstract](665) [FullText HTML](271) [PDF 977KB](21)
Abstract:
Having a closely detailed description of the nonlinear relationship between flow velocity and pressure gradient in low permeability reservoir is necessary for accurately developing the frac design, and calculating the production of a group (or unit) of wells that have been hydraulically fractured. Therefore, based on the description of the nonlinear seepage characteristics of low permeability reservoir, a nonlinear mathematical model of coupling low permeability reservoir and hydraulic fractures was established, which divided the seepage process into the nonlinear seepage stage and quasi-linearity stage according to the seepage characteristics. The Taylor expansion was used to linearize the nonlinear mathematical model, and established the finite difference equations, and then formed the computer solving model. The results of example analysis showed that the distributions of formation pressure and saturation calculated by the nonlinear mathematical model were in line with the actual situations of the stratum; the fracture flow conductivity of injection well in the fractured five-spot well pattern decreased with the formation closure, which led to poor water injection effect and low oil well production. Thus, the fracture design should be modified in accordance with the study’s results. The study results indicated that the nonlinear mathematical model and hydraulic fracture coupling could accurately describe the nonlinear relationship between flow velocity and pressure gradient in low-permeability reservoir. This breakthrough establishes a foundation to calculate the production of fractured well group in low-permeability reservoir accurately, and provides a guidance for water flooding development of low permeability reservoir.
Accurate Geosteering Technology for Deep Shale Gas Based on XRF Element Mud Logging
TANG Cheng, WANG Zhizhan, CHEN Ming, WANG Chongjing, LIANG Bo, SHI Qiang
2019, 47(6): 103-110.   doi: 10.11911/syztjs.2019135
[Abstract](596) [FullText HTML](295) [PDF 1459KB](30)
Abstract:
During drilling the deep shale gas horizontal wells in the Weirong Shale Gas Field in southern Sichuan, it is very difficult to accurately identify the marker bed, determine the bit position and judge the penetrating state of bit. To solve this problem, the X-ray fluorescence (XRF) element mud logging data was used to establish a three-terminal chart, an element intersection chart and a three-dimensional element display chart, as well as a quantitative calculation model of evaluation parameters such as rock density and gas content. The Geosteering Technology has been formed by such principle, including that fact that a three-terminal chart was used to identify the key marker beds before window-entering, the element intersection chart was used to guide the accurate window-entering of horizontal well, the three-dimensional element display chart was used to determine the penetration of the bit in a horizontal section, and the shale density and gas content etc., were used to guide the optimization of horizontal wellbore trajectory. This technology has been applied in 18 horizontal shale gas wells in the Weirong Shale Gas Field, with the average drilling rate of the target up to 98.06%. Research results showed that the technology could improve the rate of encountering high-quality reservoirs by accurately identifying the marker bed, determining the bit position and judging the penetrating state of the bit.
A Method for Identifying Abnormally Compacted Strata Based on the Fluctuation of Interval Transit Time Data
XI Pengfei, YANG Minghe, GUO Wangheng, SHI Jiangang
2019, 47(6): 111-115.   doi: 10.11911/syztjs.2019136
[Abstract](400) [FullText HTML](223) [PDF 1702KB](33)
Abstract:
The fluctuation of interval transit time data can be caused by factors such as variable formation lithology which affects the accurate identification of abnormally compacted strata by interval transit time. Therefore, the fluctuation of interval transit time data in normally compacted sections was analyzed according to the relationship between the interval transit time and well depth at normally compacted mudstone section, by eliminating the invalid data points using a density data clustering method, made possible by means of wavelet theory and the probability analysis method. Research results showed that the density clustering method could effectively remove the anomalous data points. One wavelet decomposition could meet the requirement to describe the fluctuation of interval transit time data at the normally compacted section; the distribution fitting test indicated that the fluctuation of interval transit time data was consistent with tLocation–Scale probability distribution. Thus the abnormally compacted section could be quantitatively identified by constructing a probability calculation formula. The calculation results showed that the abnormally compacted section could be quantitatively identified by calculating the fluctuation probability of interval transit time, improve the identification accuracy of abnormally compacted section, and avoid the blindness and randomness of analysis. Similar analyses can be performed for other conventional logging data analyses based on the normal compaction curve of shale.
Rapid Sinusoidal Fitting Method for Near-Bit Gamma Imaging While Drilling
ZHENG Yiting, FANG Fang, WU Jinping, QIAN Deru, ZHANG Wei
2019, 47(6): 116-122.   doi: 10.11911/syztjs.2019101
[Abstract](778) [FullText HTML](321) [PDF 1416KB](43)
Abstract:
Seeking to solve the problem of low transmission rate of existing LWD data and the demands on real-time gamma imaging, sector gamma-ray imaging characteristics were simulated and analyzed. This occurred while a near bit gamma-ray imaging tool crossing inclined interface moving from low-level radioactive sandstone to high-level radioactive mudstone, and thus a rapid sinusoidal fitting method based on the sector gamma imaging was proposed. Based on the studies, a rapid sinusoidal fitting firmware algorithm for near-bit gamma imaging logging was designed. This algorithm combined the least squares frequency estimation and 3-parameter sine fitting to obtain the 4 parameters of the sinusoid, such as amplitude, frequency, phase and DC component, hence obtaining the multi-sector gamma imaging through fitting inversion. By using the fast sinusoidal fitting method, the gamma data was acquired in the simulated wellbore fabricated with the standard rock samples and layered dipping strata, and the fitting of multi-sector gamma imaging measurement was realized with a small fitting error. The results showed that the sinusoidal features of the 8-sector gamma image obtained by fitting inversion were clear and they could accurately reflect the information of the inclined strata interface, which verified the correctness and feasibility of the fast sinusoidal fitting method.
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](3926) [PDF 1006KB](3999)
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](5694) [PDF 1148KB](4167)
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](3727) [PDF 1084KB](4010)
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](4198) [PDF 1210KB](3995)
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](3953) [PDF 1064KB](4457)
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](3512) [PDF 1031KB](3964)
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](3355) [PDF 1055KB](3670)
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](3478) [PDF 1084KB](4060)
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](3335) [PDF 1143KB](3722)
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](3647) [PDF 1030KB](3627)