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Analysis of Welding Technology and Weld Expansion Performance on Expandable Profile Liner
WANG Jianjun, TAO Xinghua, ZOU Yong, XUE Long
 doi: 10.11911/syztjs.2022008
[Abstract](45) [FullText HTML](14) [PDF 2035KB](11)
Because expandable profile liners (EPLs) are connected by welding, their overall expansion performance is a function of weld expansion performance. To understand the weld expansion performance, two kinds of EPL welding technologies, namely, manual welding and automatic welding, were outlined. The weld expansion process of an 8-shaped EPL with a diameter of ϕ149.2 mm was simulated by the finite-element method in light of elastic-plastic mechanics. The weld expansion performance was then analyzed and verified by EPL test well and field tests. The following results were obtained from simulation analyses and tests. The points of maximum weld stress and strain during EPL expansion occurred on the EPL outer wall. It was noted that variation laws of weld stress and strain with internal pressure were similar to those of EPL body stress and strain, although the weld stress and strain were higher than EPL body stress and strain during the whole process. The 8-shaped EPL with a diameter of ϕ149.2 mm and the weld were still in the safe range when the EPL was pressurized to 30 MPa. The mechanical expansion requirements were satisfied when the EPL was pressurized to 18 MPa by hydraulic expansion. The results showed that welds obtained by existing welding technologies could meet the field expansion requirements. The variation laws of weld stress and strain of EPL obtained by simulation were consistent with the test results. This research can guide the field application of EPLs.
Fracturing Technologies with Profile Control and Water Shutoff for Medium and High Water-Cut Wells in Ultra-Low Permeability Reservoirs of Changqing Oilfield
DA Yinpeng, LI Jianhui, WANG Fei, HUANG Ting, XUE Xiaojia, YU Jinzhu
 doi: 10.11911/syztjs.2022012
[Abstract](23) [FullText HTML](19) [PDF 2977KB](4)
Due to the influence of the high-permeability zone, the water cut will increase and reservoir stimulation results are poor when conventional refracturing is implemented in the ultra-low permeability reservoirs of Changqing Oilfield at the medium and high water-cut development stage. Focusing on the long-term injection-production development practices of typical reservoirs and infill well production data, this paper uses 3D geological modeling to analyze the stimulation mechanism of fracturing with profile control and water shutoff in medium and high water-cut oil wells. The influences of fracturing parameters on the effect of repeated stimulation were studied, and a refracturing concept hinging on “profile control and water shutoff in the pad adding stage to control water cut and dynamic multistage temporary plugging fracturing to improve single-well production” was advanced. PEG-1 gel was developed through laboratory experiments and when the mass fraction of its main agent achieved 5%-10%, gel strength would be maintained at a high level. With an optimal injection flow rate of 1.5 m3/min and an injection volume of 300-600 m3, the high-permeability zones at the fracture depth of 40-80 m could be effectively plugged. In this way, the dynamic multistage temporary plugging fracturing technology was optimized. As a result, the net pressure in the fractures was increased to above 5.0 MPa, fractures extended from the low-stress zone to the high-stress zone, and the production of the oil remaining laterally was thereby produced. Field test results showed that average daily oil production improvement per well was 1.07 t/d and water cut was reduced by 9 percentage points after the measure was implemented, which indicated that the goal of increasing oil production while controlling the water was accomplished by refracturing the medium and high water-cut wells. The proposed fracturing technology with profile control and water shutoff provides a new technical concept for the repeated stimulation of medium and high water-cut wells in ultra-low permeability reservoirs of Changqing Oilfield.
Design and Application for LWD Quadrupole Acoustic Logging Tool
LIU Xien, SUN Zhifeng, QIU Ao, LI Jie, LUO Bo, PENG Kaixuan, LUO Yulin
 doi: 10.11911/syztjs.2022058
[Abstract](39) [FullText HTML](19) [PDF 4168KB](10)
The LWD monopole acoustic tool cannot measure shear wave in soft formation, so the role of tool in formation evaluation is greatly reduced. In this paper, a LWD quadrupole acoustic logging tool (QUAST) is developed, which solves the problem of shear wave measurement. The key technologies such as acoustic transducer, isolator and receiver sonde system of the tool are all introduced in detail. And real drilling data of the tool is also analyzed. The measurement results show that this tool can measure high-quality monopole full wave and quadrupole wave, and the slowness of shear wave measured in monopole mode is consistent with the quadrupole shear wave in hard formations. The research and development of this tool has broken the technical monopoly of international service companies and will promote domestic LWD acoustic logging technology.
Preparation and field test of Binary Complex Foam Agent COG
WANG Weiheng, LU Junhua, HAN Qian
 doi: 10.11911/syztjs.2022053
[Abstract](18) [FullText HTML](11) [PDF 1797KB](1)
In view of the problems that foam agent is not suitable for high temperature and high salinity wells in Pingqiao South Area and the recovery gas by discharge water effect is not ideal, the development of foam agent(COG) suitable for the geological conditions of this area was carried out. The binary system of cocamidopropyl betaine(CAB), ammonium dodecyl dimethyl oxide(OB) and hydroxypropyl guanidine gum(Guar) were selected as raw materials to prepare the binary complex foam agent COG. According to orthogonal experimental design, the effect of mass ratio of CAB, OB and Guar on the foaming ability of binary system was studied, and The optimum addition was determined. The foaming ability, foaming stability, temperature resistance and salt resistance of COG were evaluated in the laboratory, its comprehensive performance is obviously better than the two foam agents that used in the field at 95℃, salinity is 10×104 mg/L. The field test results in 3 gas wells show that COG has a good effect of drainage gas production and stimulation, the gas production of single well is increased by more than 10% compared with the original foam agent. The results show that the binary complex foam agent COG is suitable for the foam drainage technology of shale gas Wells in Pingqiao South area, and it has good popularization and application value.
Calculation and Correction of Azimuth Error Based on Finite Element Analysis
MENG Qingwei, JIANG Tianjie, LIU Yongjing, YANG Jie, WANG Yuezhi
 doi: 10.11911/syztjs.2022031
[Abstract](22) [FullText HTML](3) [PDF 3382KB](2)
In order to meet the high precision demand of directional well magnetic direction, it is necessary to accurately understand the azimuth measurement accuracy and error sources. In this paper, the finite element analysis software is used to simulate the change of the interference magnetic field of the drilling tool in the geomagnetic field. The measurement value of the azimuth error is obtained by the three-axis magnetic induction intensity inside the drill pipe, and the azimuth error is obtained by comparing with the real azimuth of the drill pipe. The variation of azimuth error is observed by controlling the azimuth angle of drill pipe, inclination angle, bottom hole assembly, length of nonmagnetic drill collar and the size and direction of external magnetic field. Through the simulation experiment, it is concluded that the azimuth error is the smallest in the north-south direction of the drill pipe and the largest in the east-west direction of the drill pipe, and increases with the increase of the well inclination angle. This change shows a sinusoidal variation. The longitude and latitude also have an impact on the change of azimuth angle. The azimuth error increases with the increase of dimension, which mainly depends on the local total magnetic field and magnetic inclination angle. The results show that the azimuth error is closely related to inclinometer data, bottom drilling tool combination, longitude and latitude, and nonmagnetic drill collar length. The azimuth error under different conditions can be accurately estimated by finite element simulation. The simulation results can provide theoretical basis and data reference for the selection of non-magnetic drill collar and bottom drill assembly and azimuth error correction in engineering application.
Key Drilling Technologies of Well Bin 4 under the Daily Rate System Management Mode
LI Yan, HU Zhiqiang, XUE Yuzhi, LIANG Wenlong, TANG Wenquan, NIU Chengcheng
 doi: 10.11911/syztjs.2021133
[Abstract](89) [FullText HTML](59) [PDF 1484KB](14)
The daily rate system management mode highlights the leading role of Party A, thereby optimizing management procedures and and increasing the efficiency of completion operations. To promote the market-oriented operation of daily rate system management for drilling and completion, Sinopec selected Well Bin 4 as the first pilot exploratory well to use the system in China. The drilled strata of the well feature fracture-cavity development, high leakage risk, strong abrasiveness, and poor drillability, which lead to many drilling difficulties, such as being very leak-prone, highly likely to collapse and break, subject to serious bit bouncing, and low rate of penetration(ROP). In response to these drilling problems, key technologies for comprehensive and efficient drilling were developed. They are based on the formulation of ROP increase and rock breakage plans for different well sections, the optimal selection of drilling BHA(Bottom Hole Assembly) for rock breakage at different well sections, and the development of a plugging and anti-sloughing drilling fluids while strictly implementing the the daily rate system management mode which was customized for Sinopec’s drilling and completion projects. The field application revealed that breakthroughs were made in terms of operation efficiency, drilling and completion periods, complex processing, and average ROP, and there were no failures or shutdowns during drilling. With a drilling depth of 4 056 m, the drilling period, well completion period, and the average ROP of the whole well were 35.06 days, 39.79 days, and 16.04 m/h, respectively, all of which set records for exploratory well constructions in the Binchang Work Area. The research shows that the daily rate system management mode has advantages in the integrated application of new technologies and management efficiency. Moreover, the key drilling technologies and management mode of Well Bin 4 are reproducible and can be used as reference, which provide a demonstration for the market-oriented operation and promotion of the daily rate system.
Research of the Development of Digital Twin Technology in Drilling Engineering
YANG Chuanshu
 doi: 10.11911/syztjs.2022068
[Abstract](26) [FullText HTML](11) [PDF 1699KB](9)
This article briefly described the origin of digital twin technology and the research status of digital twin technology in oil and gas drilling industry, proposed key technologies such as digital twin of wellbore, digital twin of geological environment, digital twin of drilling rig, simulation of downhole dynamic process, real-time interaction of physical-digital twin, etc., Six application scenarios are designed, including pre-drilling simulation, prediction and optimization, complex well construction team rehearsal, early-warning and decision-making while drilling, remote drilling control, predictive maintenance of drilling equipment, and drilling training. Three research and development emphases of the drilling digital twin system are put forward. Finally, the difficulties and countermeasures of drilling digital twin technology are analyzed. The research results provide a technical reference for accelerating the application of digital twin technology in the field of drilling engineering and promoting the digital and intelligent transformation of drilling engineering.
Development Status and Future Trends of Intelligent Fracturing Technologies
JIANG Tingxue, ZHOU Jun, LIAO Lulu
 doi: 10.11911/syztjs.2022065
[Abstract](58) [FullText HTML](15) [PDF 2101KB](9)
With the rapid development of artificial intelligence technology and its wide implementation in the oil and gas industry, impressive progress in intelligent fracturing technologies has been achieved. These are technologies that involve the intelligent optimization of fracture and fracturing parameters, fluids and materials, equipment and tools, early warning system for fracturing risks, control of real-time fracturing parameter optimization, and fracture monitoring, etc. Despite that, a complete intelligent fracturing technology system remains to be developed due to unbalanced developed degree among those aspects.After the development status of intelligent fracturing technologies was analyzed, the development trends of intelligent fracturing were identified, including in-depth data mining of small data samples, building an intelligent decision-making platform for geological-engineering integrated fracturing based on 3D sweet spot distribution, developing intelligent responsive fracturing fluids and materials, creating a 4D intelligent monitoring model for fracture propagation and achieving visualization, and building unattended fracturing equipment and tools. All of these are crucial for developing a complete and uniform intelligent fracturing technology system and accomplishing another round of hydraulic fracturing technology innovations.
Research on a Polygonal Quartz Sand Flushing Fluid for Cementing Oil and Gas Wells and Its Field Application
HE Licheng
 doi: 10.11911/syztjs.2022064
[Abstract](37) [FullText HTML](12) [PDF 1740KB](2)
Conventional flushing fluid cannot effectively remove the filter cake from the well walls during oil and gas wells cementing, especially oil-bearing filter cakes formed by oil-base drilling fluid on the well walls and the oil film attached to the casing walls, both of which seriously affect cementing quality. Therefore, it was hypothesized that polygonal quartz sand particles with sharp corners and irregular shapes mixed into an ideal suspending agent would strengthen the physical scouring capabilities of flushing fluid. With that in mind, a polygonal quartz sand flushing fluid was prepared. The laboratory test revealed that the prepared flushing fluid was highly stable and compatible with the cement slurry and drilling fluid, and the flushing efficiency was higher than that of conventional flushing fluid by 10 to 30 percentage points. After the successful laboratory results, the prepared flushing fluid was successfully applied in four wells in Shengli Oilfield, and the cementing quality was significantly improved. The research and application indicated that the prepared flushing fluid could effectively remove the filter cake, oil film, and cuttings on the well walls and improve the cementing environment of the cement-formation interface. In this way, the cementing quality was enhanced to meet the requirements of large-scale fracturing for the cementing quality of cement sheaths.
Sand-Carrying Experiments with Supercritical CO2 in a Horizontal Annulus
SUN Xiao, WANG Haizhu, LI Yingjie, ZHENG Yong, LU Qun
 doi: 10.11911/syztjs.2021099
[Abstract](67) [FullText HTML](33) [PDF 2599KB](9)
According to the similarity principle, a device for sand-carrying tests was developed to determine the sand-carrying performance of supercritical CO2 in the horizontal annulus and analyze the effects of key operating parameters on the sand-carrying performance. The device was employed to explore the influence of the injection mass flow, sand concentration, outlet pressure, and fluid temperature of supercritical CO2 on the sand migration in the horizontal annulus. The results showed that supercritical CO2 could effectively carry sand in the horizontal annulus by means of suspension transport, and the increase in its mass flow could enhance the turbulence intensity of the fluid in the annulus and improve the sand-carrying effect by suspension transport. In a high sand concentration, sand beds were likely to occur at the bottom of the annulus, which reduced the open area and raised the sand transport velocity. Under the same injection condition, the sand transport velocity in the annulus decreased with the increase of outlet pressure, but the amplitude of reduction is gradually lowering. In addition, a rise in fluid temperature was conducive to the accumulation reduction of sand in the annulus in an appropriate temperature range. The research results can provide a reference for optimizing the key construction parameter design in drilling and fracturing with supercritical CO2.
Experimental and Numerical Simulation Study of Natural Gas Hydrate Erosion by Swirling Jet
ZHANG Yiqun, HU Xiao, WU Xiaoya, LI Gensheng, TIAN Shouceng, ZHAO Shuai
 doi: 10.11911/syztjs.2022046
[Abstract](37) [FullText HTML](12) [PDF 3959KB](8)
In order to explore an efficient development mode suitable for the characteristics of natural gas hydrate in the South China Sea, the hole forming law of submerged conical jet and swirling jet on natural gas hydrate sediments under confining pressures were compared and analyzed. Firstly, the Lagrangian-Eulerian (ALE) fluid-solid coupling model was established with LS-DYNA software to analyze the influence of submerged and confining pressure environment on the erosion efficiency of the two types of jets on natural gas hydrate sediments. The experiments for natural gas hydrate generation and jet erosion were carried out based on a self-designed visual experimental device. After the secondary generation of natural gas hydrate, gypsum was injected into the erosion hole to measure the depth and size of erosion hole. Through comparative analysis of numerical simulation and experimental results, it is concluded that the confining pressure can increase the strength of natural gas hydrate sediments while inhibiting the diffusion ability of jet, and can reduce the jet erosion efficiency. In the environments without confining pressure and with a confining pressure of 5 MPa, the volume of natural gas hydrate sediments eroded by swirling jet is 1.8 and 1.7 times that of conical jet, respectively. The results show that, for the natural gas hydrate deposits in argillaceous silt reservoirs, the swirling jet has a stronger hole-expanding ability than the conical jet while ensuring the depth of the erosion hole. This study provides a theoretical basis for the production of natural gas hydrate by solid fluidization method.
“Casing in Casing” Mechanical Isolation Refracturing Technology in Fuling Shale Gas Wells
LIU Yaowen, MING Yue, ZHANG Xudong, BIAN Xiaobing, ZHANG Chi, WANG Haitao
 doi: 10.11911/syztjs.2022010
[Abstract](25) [FullText HTML](12) [PDF 2223KB](4)
The application of temporary plugging and diverting refracturing in Fuling Shale Gas Field brought on technical difficulties accompanied by poor production increase. To solve this problem, this paper analyzed principles and characteristics of technologies used in shale gas wells abroad. They included temporary plugging and diverting refracturing, and mechanical isolation refracturing. What was found was that that mechanical isolation could completely block the perforations and precisely control fracture initiation of hydraulic refracturing. From that, the “casing in casing” mechanical isolation refracturing technology took shape. In Fuling Shale Gas Field, this technology was tested with a casing (outer diameter of 88.9 mm) inserted into the other one (inner diameter of 115.0 mm) where in a new and closed well casing was formed. In addition, refracturing technologies targeted for different residual oil distribution in the reservoir were developed through studies. In the original well casing, attention should be paid to exploring the residual oil among fractures in the stimulated well section. At the same time,emphasis should target the poorly stimulated sections, to see how to recover the flow conductivity of the fractures. After implementing that technology in Well JYAHF, the recoverable reserve for a single well increased by 0.36×108 m3, and the recovery efficiency increased by 4.8%. The study shows that the “casing in casing” mechanical isolation refracturing technology can significantly improve the result of stimulation and provide technical support for long-term and efficient shale gas field development in China.
Adaptive stress sensitivity analysis of fractured heterogeneous tight reservoir
LI Hong, YU Haiyang, YANG Haifeng, DENG Tong, LI Xu
 doi: 10.11911/syztjs.2022054
[Abstract](39) [FullText HTML](15) [PDF 2580KB](2)
The fractured tight reservoir is characterized by strong heterogeneity and stress sensitivity. To determine the influence of stress sensitivity on production matrix and fracture in heterogeneous reservoir, a numerical model taking into consideration both the stress sensitivity of heterogeneous matrix and multi-scale fractures was established, which combined stress sensitivity quantitative characterization model, and embedded discrete fracture model based on projection. The model can obtain the adaptive stress sensitive characteristic curves according to the reservoir physical property difference. The results show that the stress sensitivity of matrix can’t be ignored in the highly heterogeneous tight reservoir, and the stress sensitivity has a great influence on production in the early stage, mainly caused by fracturing fractures. With the progress of production, it gradually transitioned to natural fractures and matrix, and the stress sensitivity of reservoir gradually decreased. Excessive production pressure difference will cause stress damage to the reservoir, which is not conducive to long-term production. In addition, the distribution pattern of multi-scale fractures with different filled pattern in the reservoir also has a direct impact on productivity. When the fractures are less filled, it is larger in scale and can bring about higher productivity. The research results can provide theoretical basis for reasonable production arrangement and developing plan optimization of tight fractured reservoirs.
Optimization and field application of secondary reformation technology for coalbed methane Wells
LIANG Zhifei, LIU Changsong, ZHEN Huaibin, ZHAO Haifeng, WANG Chengwang
 doi: 10.11911/syztjs.2022067
[Abstract](24) [FullText HTML](8) [PDF 2131KB](12)
The coalbed methane resources is rich in China, but the capacity of coalbed methane Wells in some areas is not fully released and cannot support long-term stable and high production. In order to further optimize the secondary fracturing technology of coal reservoir and transform low energy CBM Wells, and improve the production of CBM Wells. Taking Hancheng block as an example, on the basis of analyzing the geological characteristics of the block, the reasons for low production of conventional secondary fracturing test Wells were analyzed. In view of the technological defects and technical problems in the construction process of secondary fracturing, the fracturing design idea of coalbed methane well was proposed to solve the "coal powder plugging fracture + new fracture extension distance is limited" as the main goal, so as to form the new technology of "acidification + temporary plugging" compound secondary fracturing and 3 Wells were tested in the field. The results showed that the composite secondary modification process had good adaptability to low production CBM Wells. The productivity of J4 test well was greatly improved and the fracture volume was ideal. The J5 and J6 test Wells were restored to production capacity with high production potential. The technology can be used as a reference for the old CBM well reconstruction in this area and under the same geological background.
Simulation Research on Influencing Factors of Stabilization Platform for Mechanical Vertical Drilling Tools
LI Ranran, ZHANG Kai, CHAI Lin, ZHANG Long, LIU Baolin
 doi: 10.11911/syztjs.2021106
[Abstract](36) [FullText HTML](30) [PDF 2934KB](1)
As the automatic vertical drilling tool equipped with a mechanical stable platform requires no electronic components and possesses good high-temperature resistance with low costs, it is a good choice for deviation prevention in deep well drilling. However,it has difficulty in further improving the deviation correction accuracy of the tool. Therefore, according to its dynamic characteristics, two mechanical stable platform models: a theoretical analytical one, and Adams dynamic simulation one were built on the basis of a typical stable platform structure and its working principle. Then, theoretical calculations and simulation calculations were conducted to study the factors affecting the performance of the stable platform, and the main influencing factors and laws governing the performance of the mechanical stable platform were determined. The research results revealed key performance influencers, which included the length, the inner and outer radius of the eccentric block, the inclination angle, and the dynamic friction coefficient between disc valves.Based on the results, the optimization direction and recommended value of the structural parameters of the mechanical stable platform were also summarized, and they can provide a reference for further design optimization for automatic vertical drilling tools with mechanical stable platforms.
The Research and Application of Slick-Water and Gelling-Liquid Integrated Fractring Fluid
WEI JuanMing
 doi: 10.11911/syztjs.2022063
[Abstract](10) [FullText HTML](7) [PDF 2029KB](0)
Withtheincrease in shale-gas and tight sand production inpastdecade, slick-water-fracturing fluids became more prevalent. The rapid-viscosifyfrictionreducing polymer represents the essential component in slick-water-fracturing fluid. Inthisarticle, the friction reducing polymer thickener for the slick-water and gelling-liquid integrated fracturing fluid was prepared by emulsifiedsolution polymerization, AM, AA and AMPS were used as raw materials,whichwassynthesized by redox initiator system.Cleanupagentand clay stabilizer agent with good compatibility and synergistic effect were developed, combinedwithfriction reducer to form the slick-water and gelling-liquid integrated fracturing fluid formula. The viscosity of slick-water and gelling-liquid fluid are 2-40 mPa.s and 50-120mPa.s.The high-temperature stability of the fluidcouldtolerated with 160℃, the maximum friction reduction rate can reach 83%, the performanceofsand carrying capacity is excellent, and the sand concentration can up to 10-43%, which could be adjust by continuously mix procedure and reach viscosity demanding. The integrated fracturing fluid has been applied in Sichuan Basin and Shengli Oilfield. The friction reduction and sand carrying capacity performance well at field test.
A Calculation Method of Perforation Limit of the Strong Water-Flooded Layer in the Period of High Water Cut in Offshore S Oilfield
GE Lizhen, WANG Gongchang, ZHANG Rui, ZHANG Lie, ZHANG Junting
 doi: 10.11911/syztjs.2022013
[Abstract](24) [FullText HTML](8) [PDF 2368KB](1)
After long-term water drive development in S Oilfield, strong water flooded intervals have increased significantly. The traditional water flooded layer division method and corresponding perforation principle can not meet the development needs of the current stage. Therefore, based on the indoor physical model test and logging interpretation results, using the seepage resistance coefficient and the quantitative evaluation method of low efficiency injected water, this paper analyzes the dynamic interference limit caused by the difference of oil displacement efficiency, and puts forward the classification type of water flooding level suitable for s Oilfield in high water cut stage. On this basis, the perforation principle based on the differential limit of oil displacement efficiency is put forward. The results show that when the oil displacement efficiency is greater than 30%, the interlayer interference caused by the difference in water cut is small, and when the oil displacement efficiency is 40%~45%, the low efficient or ineffective degree of water circulation is aggravated. Based on the above two types of limit, the water-flooded degree of oil field in the stage of high water cut can be divided into six levels. When the flooding level is from I to V, there is no need to avoid perforating except for engineering factors. And when the flooding level is VI, this kind of water-flooded layer should be abandoned. This method has guided the formulation of perforation scheme of adjustment wells in S oilfield. After the implementation of several adjustment wells, the water cut has decreased by 8% on average, and good results have been achieved..
Cementing Technology Using a Nitrogen-Filled Foamed Cement Slurry for Horizontal Shale Gas Wells in the Eastern Chongqing Area
KUANG Lixin, TAO Qian
 doi: 10.11911/syztjs.2021103
[Abstract](4) [FullText HTML](1) [PDF 2814KB](0)
Normal pressure horizontal shale gas wells in the eastern Chongqing area are prone to leakage during the process of production casing cementing, and often encounter sustained casing pressure (SCP) after staged fracturing. To solve these technical difficulties, this paper studied the cementing technology of mechanical nitrogen-filled foamed cement slurry. Foaming agents and foam stabilizers were selected in the design of low-density foamed cement slurry. Based on the high-pressure gas equation of state, the whole-process pressure balancing of foamed cement slurry and the design of the slurry column structure were performed, and a density calculation model of foamed cement slurry under wellbore pressure was built. In this way, a cementing technology using mechanical nitrogen-filled foamed cement slurry was developed. Specifically, the density of low-density foamed cement slurry ranged from 0.80 to 1.55 kg/L, and the half-life of foam in cement slurry was 33.8 h, with the elastic modulus of foamed cement paste being 4.6 GPa. The residual strain of foamed cement paste under cyclic loading was 0.21%, which demonstrated its good mechanical properties. The whole-process pressure-balancing cementing technology and the slurry column structure design of low-density foamed cement with staged gas injection could meet the requirements of cementing for leakage prevention. When the technology was applied to 20 horizontal shale gas wells in the eastern Chongqing area, no leakage occurred during the construction process, with an excellent rate of cementing quality of 100%, and there was no SCP after fracturing. Research and field applications indicate that the cementing technology using mechanical nitrogen-filled foamed cement slurry can solve the leakage problem of horizontal shale gas wells in the eastern Chongqing area during the production casing cementing, and the foamed cement paste has good elastic deformation, which can prevent SCP after fracturing.
Low-Cost Fracturing Technology in Normal-Pressure Shale Gas Reservoirs in Wulong Block
ZHOU Bocheng, XIONG Wei, LAI Jianlin, FANG Qilong
 doi: 10.11911/syztjs.2022011
[Abstract](52) [FullText HTML](16) [PDF 2199KB](5)
Normal-pressure shale reservoirs in Wulong Block have low energy and production, and suffer from difficulties in beneficial development. For this reason, a low-cost fracturing technology was studied for its development. Considering difficulties of fracturing stimulation in Wulong Block, induced stress calculation, fracture simulation, and fracturing cost comparisons were carried out. This allowed the fracturing length, number of clusters, and operation parameters to be optimized. Further, the fracturing materials and equipment were chosen. A new fracturing technology was thereby developed, involving a short fracturing length, a single-cluster sleeve, low-viscosity slick water, low-cost quartz sand, continuous sand addition at a high proppant concentration, which was then applied in the field test on Well A in Wulong Block. Through the application of the unlimited sleeve completion and the real-time adjustment of on-site fracturing parameters, the production of Well A after fracturing was comparable to that of the fracturing well on the same platform with fracturing parameters of a medium fracturing length, tight spacing, and a ceramic proppant. In this study, the fracturing cost was reduced by 52.8%, and the fracturing performance sped up to 8 stages per day. The low-cost fracturing technology hasprovided technical reference for the beneficial development of normal-pressure shale gas in Wulong Block.
Analysis and Numerical Simulation of Acoustic Advance Ranging in Gas Drilling
JIAN Xu, LI Gao, WANG Jun, HAN Xu, HUANG Bing, WANG Songtao
 doi: 10.11911/syztjs.2022016
[Abstract](46) [FullText HTML](18) [PDF 3558KB](6)
The safety of gas drilling is greatly affected by the geological conditions of reservoirs, and due to the influence of noise generated by gas, it is difficult to recognize the formation reflection signals in gas drilling. Therefore, a near-bit impact source sub while drilling was designed, and a method of acoustic advance detection for gas drilling was proposed on the basis of the self-excitation and self-reception principle of seismic waves and the deduction of ranging formulas. In this way, the detection accuracy could be raised, and the uncertainty of lithological interfaces ahead of the bit could be reduced while drilling. Specifically, the attenuation effect of polytetrafluoroethylene (PTFE) on vibration coda waves was analyzed through an impact test; the feasibility of the acoustic advance detection method in gas drilling was verified through numerical simulations, and the influence of detection distance on the amplitude of reflected waves was analyzed. The impact test revealed that the coda waves of vibration waves on the hollow cylinder were significantly attenuated upon the use of PTFE; the numerical simulations indicated that the boundary conditions of a perfectly matched layer (PML) could effectively eliminate the interference of boundary reflection of the model, and the ranging error calculated by the arrival time of reflected P-waves was 1 m. Additionally, with the increase in detection distance, the relative intensity of reflected P-waves saw a gradual increase, and the amplitude of reflected waves decreased greatly. The research results verify the feasibility of detecting lithological interfaces ahead of the bit by near-bit impact sources and provide a new idea for the development of acoustic advance detection technology while drilling in gas drilling.
The Effect of Rock Breaking Test by Plasma Torch and the Suggestion of Field Application
YU Yan, GAO Rui, JIA Yudan, QIAO Lei, ZHOU Wei
 doi: 10.11911/syztjs.2022034
[Abstract](37) [FullText HTML](23) [PDF 2158KB](2)
When drilling for deep geothermal energy in hot dry rock or when drilling for deep oil and gas, there are some unsolved issues, such as extraordinary rock hardness and low drillability,it is difficult to improve drilling efficiency by using traditional drilling technology.To solve this problem,explore a drilling technology by plasma torch.Analysis the principle of rock breaking by plasma torch,the way of rock breaking by a plasma torch, spallation and melting and evaporation.Different thickness granite and basalt rock samples were tested by plasma torch, the plasma torch can burn through the basalt with the thickness of 50mm, burn through the granite with the thickness of 30mm; but cannot burn through thicker rock samples.Combined with the test results,analyze the problems existing in field application,give the research and development suggestion.The results of this study,it can provide reference for the research and application of the drilling by plasma torch in deep hard stratum.
Balanced Off-Bottom Cement Plug Technology in Ecuador
LI Wandong, WU Yang, LAN Xiaolin
 doi: 10.11911/syztjs.2022032
[Abstract](20) [FullText HTML](10) [PDF 1977KB](2)
Aiming at the problem of low success rates of setting cement plugs in Ecuador, various factors affecting the stability and quality of a cement plug during setting are considered. In view of the instability of the interface between the cement plug and the lower drilling fluid, high-strength, low-density cement slurry and reactive viscous-pill were developed; for the cement plug quality problems caused by the narrow annulus gap between drill pipe and wellbore, a stinger tool was designed; to overcome the downward spraying of cement slurry and serious mixing with drilling fluid caused by the open shoe in the end of drill pipe, developed a flow diverter; for lack of drill pipe internal isolation plugs and the high cost, complex operation of existing wiper darts, the sponge balls were developed. Indoor test results show that the density of high-strength, low-density cement slurry is 1.74 kg/L, the 24h compressive strength is 22.5 MPa, which meets the requirements of a good cement plug; the reactive viscous-pill, its density is 1.44 kg/L, yield of point is 48 Pa and gel strength is 49 Pa, which can effectively support the upper cement slurry. Through targeted structural design, new tools such as stinger, flow diverter and sponge balls can solve the quality problems of cement plug during setting. The above-mentioned balanced off-bottom cement plug technology which has been applied in the eastern oilfield, Ecuador. The effect is good and the cement plug success rates can be greatly improved.
Bridge Concentric Downhole Constant Flow Stratified Water Injection Technology
YANG Lingzhi, ZHOU Zhiping, YANG Haien, JI Zhenning
 doi: 10.11911/syztjs.2022051
[Abstract](30) [FullText HTML](12) [PDF 2149KB](6)
In view of the problem that the qualified rate of separate layer water injection drops rapidly due to the pressure fluctuation of low permeability reservoir in Changqing Oilfield, the automatic adjustment mechanism of small volume water nozzle is innovatively designed, based on Bernoulli principle, through theoretical analysis and laboratory experiment, the automatic regulating mechanism is integrated with the bridge type constant-current stratified water distributor, which relieves the variation range of stratified flow caused by pressure fluctuation, the design parameters of the auto-adjusting mechanism are optimized to achieve the stratified and constant flow water injection with small flow rate. Laboratory experiments show that the automatic adjustment mechanism can achieve the adjustment range of 0.2−1.5 MPa. More than 40 wells have been used in Changqing Oilfield, and the pressure of water injection system has been increased within 1.5 MPa without manual intervention, after 6 months, the qualified rate of sub-injection is raised from 43.4% to 75.0% , which can reduce half of the survey and adjustment work, and the annual operation cost of a single well is reduced by 26 000 yuan. The bridge type constant flow separate layer water injection technology can effectively improve the qualification rate of separate layer water injection, prolong the period of separate injection well logging and adjustment, and provide a more efficient separate layer water injection method for fine water injection development of low permeability reservoir.
Working characteristic analysis and test of pulsating torsional impact drilling tool
WANG Wei, LIU Gonghui, LI Jun, ZHA Chunqing, LIAN Wei, XIA Mingli
 doi: 10.11911/syztjs.2021101
[Abstract](34) [FullText HTML](21) [PDF 2597KB](4)
The stick-slip vibration of PDC bit in deep hard formation restricts its speed-up effect in hard formation. To improve rock-breaking efficiency and prolong the life of bit, a pulsating torsional impact drilling tool that can provide a circumferential impact load for the PDC bit was designed. Based on the structure design and working principle analysis, the calculation models of circumferential torque and impact energy were established. The working characteristics of the impact tool under vertical well were studied. The calculation results show that the circumferential torque increases with the flow rate and decreases with the nozzle diameter. The impact energy increases with the string torque and deflection angle, decreases with the weigh-on-bit. Laboratory tests show that the structural design of the tool is reasonable, and it can realize high-frequency torsional impact, and the working frequency, pressure drop, and circumferential torque of the tool increase with the flow rate. The research results provide a theoretical foundation and guidance for field application of the tool.
Study on Calculation Accuracy of Numerical and Analytical Models for Wellbore Temperature in Ultra-Deep Wells
ZHAO Xiangyang, ZHAO Cong, WANG Peng, LIANG Xiaoyang, YANG Mou
 doi: 10.11911/syztjs.2022035
[Abstract](28) [FullText HTML](16) [PDF 1973KB](2)
Accurate prediction of wellbore temperature during drilling process is the key factor for scientific evaluation of wellbore flow safety and pressure control. Based on energy conservation principle of differential unit for wellbore and formation in this study, the transient heat transfer model and quasi-steady state heat transfer model of each control area for wellbore and formation were developed, which are solved by fully implicit finite difference method and analytical method, respectively. Combining with the well structure and drilling parameter of a deep well in Shunbei oil field, the heat transfer mechanism and the influence factor of calculation results for two mathematical models are analyzed. The results indicated that the annular fluid temperature in the lower section is lower than the initial geothermal temperature, while the fluid temperature in the upper section is higher than that temperature. In the analytical model, the heat transfer from the distant formation to the borehole wall is simplified as the dimensionless time function, and the amount of heat exchange in the formation-annulus as well as annulus and inside drill string are described as the comprehensive heat transfer coefficients, decreasing the heat exchange between the wellbore and formation, further leading to the fluid temperatures in the annulus and drill string of the analytical model lower than those of numerical model. The calculated result of transient heat transfer model is in good agreement with the measured values, and the errors of numerical and analytical models are 1.46% and 6.94%, respectively, difference value of 13.15 ℃. The research results provide analytical means for the in-depth understanding of the heat transfer mechanism and accurate evaluation temperature in drilling.
Tight Plugging Water-based Drilling Fluid Technology for Brittle Shales in Junggar Basin
Liu Junyi, Chai Jinpeng, Li Guangquan, Wang Baotian
 doi: 10.11911/syztjs.2022022
[Abstract](22) [FullText HTML](5) [PDF 2295KB](1)
In order to solve the wellbore instability problems of brittle shales in Junggar Basin, according to the multivariate cooperation principle for wellbore stabilization, wellbore strengthening principles of multi-scale tight plugging were investigated, and multi-scale tight plugging water-based drilling fluids (YHDF-1, YHDF-2) were optimized based on the mineral compositions and micro-structure characteristics of brittle shales. It was proved that wellbore instability of brittle shales was closely related to its multi-scale pore structure characteristics, and micro-fractures and nano-scale fissures were the main controlling factors, and enhancing sealing performance of drilling fluids to plug nano-scale fissures and micro-fractures was key point to solve wellbore instability of brittle shales in Junggar Basin. What’s more, improving shale hydration inhibitive ability and providing the effective stress support of reasonable drilling fluid density were beneficial to wellbore stability of brittle shales. Laboratory experimental results showed that the PPA filtration volume using 400 mD sand disc of YHDF-1 and YHDF-2 drilling fluids were only 17.8 mL and 13.2 mL and the reduction rate of shale permeability were above 90% with high temperature resistance up to 150 ℃. YHDF-1 and YHDF-2 drilling fluids were applied in the drilling operation of D-72 well and D-12 well in Junggar Basin. Field tests showed that YHDF-1 and YHDF-2 drilling fluids exhibited excellent wellbore strengthening performance with the electrical logging measurement success rate of 100% and average hole enlargement rate of 6.78%. The feasibility of tight plugging water-based drilling fluid technology was finally proved, which could provide a novel technical measure for the further study of brittle shale wellbore stability technology in Junggar Basin.
Casing Window Milling with a Single-trip Technology in Offshore Oilfield
XUE Xianbo, ZHANG Chengcheng, ZHANG Baokang, ZHANG Wenbo, QU Yue
 doi: 10.11911/syztjs.2021102
[Abstract](25) [FullText HTML](6) [PDF 1867KB](12)
The paper introduced key technology and field application of single-trip casing exit window in Bohai Oilfield. With regard to technical problems encountered in conventional milling windows, such as difficulty in passing high dog leg wellbore, multiple downhole trips required, easily deviated guide slope of mill, the China Oilfield Services Ltd (COSL) has successfully designed specifically milling tools, which can realize whipstock running, setting and window milling in the same trip. The five periods during window milling process were discussed, reference values of milling parameters (including weight on bit, rotational speed and displacement) in corresponding operational process were also given. Furthermore, this paper analyzed a filed case of sidetracking operation in an old well, and provided several suggestions on complex issue treatment during sidetrack. Since 2016, the COSL has provided casing exit window service for more than 200 wells in Bohai oilfield with average window milling periods of 10.5 h, window repairing periods 2.6 h, and successful rate 100%. Compared with two trips, the average window opening time is saved by 2.4 hours, and efficiency is improved by 22.8%. The research and field application show that the successful development of single-trip casing window tool provides a reference and guiding significance for the casing window of offshore oilfields in the future.
Development of Pulse Discharge Shock Wave Device for Shale Gas Production Increase
HUANG Kun, LI Xinyang, ZHU Xinlei, MENG Qingyang, ZENG Fanhui
 doi: 10.11911/syztjs.2022049
[Abstract](24) [FullText HTML](14) [PDF 2451KB](0)
In order to further promote the application of pulse discharge shock wave technology in shale gas production increase, a set of pulse discharge shock wave device that can be used for shale gas downhole operation is designed and developed. The device includes a ground power system and downhole energy storage and discharge systems. The downhole part is enclosed in a stainless steel cylinder with an outer diameter of 102.0 mm, and has good insulation performance and mechanical strength. The device is designed a maximum voltage of 10 kV and maximum energy storage of 5 kJ, and can repeatedly discharge more than 4000 times in a single downhole trip. Key technical points such as energy storage method, load electrode and capacitance were studied, and debugging experiments such as unblocking and rock sample fracturing were carried out on the ground, and the downhole test was carried out in the oil well. Ground experiments show that the device has strong working stability, has the effect of unblocking and rock fracturing , and can play a role in oil and gas production increase. After oil well tests, liquid production and oil production were increased by 227% and 197% respectively, showed good effect of production increase. The research believes that the device has strong working stability, has the effect of unblocking and rock fracturing , and it is also feasible to be applied to shale gas production increase, but the specific effect in shale gas is still to be further researched.
Along-String Measuring Technique and Its Development Direction
WANG Minsheng, GENG Lidong, GUANG Xinjun
 doi: 10.11911/syztjs.2022001
[Abstract](40) [FullText HTML](16) [PDF 1583KB](8)
In deep, ultra deep and complex formation and deep-water oil and gas reservoirs, the drilling operation has the characteristic of difficulty, long cycle length and frequent accident. It is of great significance for safe, efficient and fast drilling to monitor the parameters such as temperature and pressure in the well in real-time. The paper introduces the systematic composition of the along-string measuring technology of the NOV Company. The application in such scenarios as wellbore cleaning monitoring, sticking position judgement, drilling fluid leakage position judgement, leakage and formation integrity test, kick detection and drilling string and bit operation condition analysis is analyzed. The along-string measuring technology will develop in three directions. Firstly, the MWD interpretation model and application scenarios should be modified. The data mining technology and multi-parameter visual intelligent display technology should be improved. Secondly, the sensor network distribution should be optimized. The high-speed information transmission network should be developed to replace the cabled drill pipe to improve the economic benefit. Finally, more application scenarios should be extended. It is suggested that we should improve the downhole engineering parameters measuring system continuously and promote the commercial application of the cabled drill pipe technology in China. With the maturity of these two technologies, the distributed measuring transmission technology should be realized gradually. Moreover, it is a low-cost along-string measuring technology that is worth discussing to combine the conventional drill string system, the modified distributed drill string measuring tools and the smart microsphere time sharing transmission technology to realize the distributed measuring transmission.
2022, 50(2).  
[Abstract](80) [PDF 19158KB](47)
2022, 50(2): 1-2.  
[Abstract](87) [FullText HTML](33) [PDF 367KB](39)
Expert Viewpoint
Progress and Prospects of Digitization and Intelligentization of CNOOC’s Oil and Gas Well Engineering
LI Zhong
2022, 50(2): 1-8.   doi: 10.11911/syztjs.2022061
[Abstract](180) [FullText HTML](105) [PDF 1991KB](100)
The digitization and intelligentization of oil and gas well engineering are of great significance for increasing the productivity of oil and gas wells, reducing operation and drilling costs, as well as improving the health, safety, and environment (HSE) management level. During the Thirteenth Five-Year Plan period, CNOOC has completed its overall layout for the digitization and intelligentization of oil and gas well engineering through theoretical innovation and scientific research. As a result, preliminary achievements have been made in intelligentized operation, collaborative design, and refined management. This paper presents the achievements regarding the digitization and intelligentization of CNOOC’s oil and gas well engineering in detail, including eDrilling system, big data analysis system of drilling parameters, downhole drilling parameter measurement and short signal transmission system, early overflow monitoring system for deepwater drilling, downhole fiber optic monitoring system, drilling and completion integrated design platform, drilling and completion data submission system, information display system, and data analysis system, etc. To address information islands and the shortage of inter-disciplinary talents in intelligentization, the paper points out the necessity of adhering to the philosophy of "making them work for us instead of just being owned by us" while dealing with technologies in digitization, and actively seeks for deep strategic cooperation in the field of oil and gas well engineering with corporations specialized in advanced internet and intelligentization in China and other countries. In addition, it emphasizes independent innovation capabilities and bringing together "enterprises, universities, research institutes, and end-users" to promote the steady improvement of the research and application in regard to the digitization and intelligentization of CNOOC’s oil and gas well engineering so as to boost the high-quality development of the offshore oil industry in China.
Special Report of Shale Oil Engineering Technology
Horizontal Well Volumetric Fracturing Technology Integrating Fracturing, Energy Enhancement, and Imbibition for Shale Oil in Qingcheng Oilfield
ZHANG Kuangsheng, TANG Meirong, TAO Liang, DU Xianfei
2022, 50(2): 9-15.   doi: 10.11911/syztjs.2022003
[Abstract](138) [FullText HTML](89) [PDF 1885KB](58)
Shale oil reservoirs in Qingcheng Oilfield have distinct characteristics of low pressure and low brittleness index, which significantly hinder the establishment of an efficient displacement seepage system after volumetric fracturing. In light of this, a volumetric fracturing technology was developed integrating fracturing, energy enhancement, and imbibition. A new method for refined and detailed classification of shale oil reservoirs was formulated. Then, stimulation strategies for different reservoir types were optimized with field big data obtained from tests on long-term fluid production profiles. Finally, the key parameters of the volumetric fracturing technology integrating fracturing, energy enhancement, and imbibition were optimized through the numerical simulation of oil reservoirs. The research results showed that type Ⅰ and type Ⅱ reservoirs, making up 83.6% of the stimulated sections and 95.5% of the total production, were the main contributions to productivity. In contrast, the productivity contribution of type Ⅲ reservoirs accounted for only 4.5% of the total production. Therefore, stimulation treatment priority should be given to type Ⅰ and type Ⅱ reservoirs while only some selective sections of type Ⅲ reservoirs should be stimulated. The optimal intervals of fluid injection intensity for type I and type II reservoirs are 20–25 m3/m and 15–20 m3/m respectively, with synchronous energy enhancement. The volumetric fracturing technology was applied to more than 200 horizontal shale oil wells in Qingcheng Oilfield. The initial single-well production was increased from 9.6 t/d to 18.0 t/d, the single-well annual cumulative oil production was enhanced from 2 380 t to 5256 t, and the single-well estimated ultimate recovery (EUR) was improved from 1.8×104 t to 2.6×104 t. This technology has provided a technical reference for the efficient development of similar unconventional shale oil reservoirs.
Lost Circulation Prevention and Plugging Technologies for the Ultra-Long Horizontal Section of the Horizontal Shale Oil Well Hua H90-3 in Changqing Oilfield
SUN Huan, ZHU Mingming, WANG Weiliang, LI Zhijun, CHEN Ning, LIU Bin
2022, 50(2): 16-21.   doi: 10.11911/syztjs.2022004
[Abstract](170) [FullText HTML](71) [PDF 1646KB](56)
Well Hua H90-3 is an ultra-long horizontal well deployed in the Longdong National Shale Oil Demonstration Area in Changqing Oilfield. Due to geological migration, the horizontal section of the well has a discontinuous reservoir with faults in it. The pores of sand bodies are well developed, and the pressure-bearing capacity of the formation is low. In addition, formation fluids are active, and the plugging fluid cannot be retained or solidified after dilution, which increases the difficulty in plugging. In view of the above technical difficulties, the equivalent circulating density (ECD) monitoring technology was applied to prevent lost circulation in advance, and the plugging while drilling technology was incorporated to improve the efficiency of plugging. Moreover, curable and water-blocking fibrous working fluids for lost circulation control were developed to achieve the one-time sealing of the thief zone in combination with the precise positioning technology, so that the key technologies of lost circulation prevention and plugging were formed for the ultra-long horizontal sections of shale oil. The on-site application of the technologies made possible the successful drilling of Well Hua H90-3, with a horizontal section length of 5 060 m, which set a new record for the longest horizontal section of onshore horizontal shale oil wells in Asia. The research showed that the technologies could provide a technical reference for the drilling of horizontal shale oil wells with ultra-long horizontal sections in China.
Experimental Study on Foam-Assisted Gas Huff-and-Puff in the Jimsar Shale Oil Reservoir
XIONG Xiaofei, SHENG Jiaping
2022, 50(2): 22-29.   doi: 10.11911/syztjs.2022017
[Abstract](78) [FullText HTML](30) [PDF 2516KB](21)
Due to the fact that the Jimsar shale oil reservoir has low permeability and massive artificial and natural fractures, and gas channeling easily happens when N2 huff-and-puff is adopted for development, there is a problem of limited sweep range of N2 and low shale oil recovery. For a greater sweep range of N2 and enhanced oil recovery (EOR) in the Jimsar shale oil reservoir, the Jimsar shale samples were used for foam-assisted gas huff-and-puff experiments based on the evaluation of plugging capacity of foam for shale fractures. Besides, the team analyzed the EOR mechanism of foam-assisted gas huff-and-puff, and studied the influence of the huff-and-puff rounds and matrix permeability of fractured shale samples on the oil recovery by foam-assisted gas huff-and-puff. The experimental results showed that foam could seal fractures and effectively inhibit gas channeling, and when the foam volume fraction was 50% and the gas injection rate was 2 mL/min, the breakthrough pressure could reach the maximum value, with the best effect of plugging. Compared with N2 huff-and-puff, the foam-assisted gas huff-and-puff can improve the recovery of crude oil not only from the large and medium pores, but also from micropores. With optimal foam injection parameters, the recovery of fractured samples increase with the rounds of huff-and-puff, but the increasing extent will gradually fall. For fractured samples with high matrix permeability, the recovery of foam-assisted N2 huff-and-puff are also high. The results can provide the guidance for the development of the Jimsar shale oil by foam-assisted gas huff-and-puff.
Fracturing Parameters Optimization of Horizontal Wells in Shale Reservoirsduring "Well Fracturing-Soaking-Producing"
CHEN Zhiming, ZHAO Pengfei, CAO Nai, LIAO Xinwei, WANG Jianan, LIU Hui
2022, 50(2): 30-37.   doi: 10.11911/syztjs.2022005
[Abstract](207) [FullText HTML](83) [PDF 3651KB](71)
Regarding the absence of a systemic and complete method for optimizing the multi-stage fracturing parameters of horizontal wells in shale reservoirs during well fracturing-soaking-producing, a fracturing parameter optimization method was developed based on the dynamic inversion theory. First, a numerical model (EDFM-NM) for horizontal wells was established depending on the complex induced fracture networks formed in hydraulic fracturing of shale oil reservoirs, which takes into consideration the characteristics of the reservoirs as well as complex natural fractures. With the model, solution for the pressure of reservoirs with discrete natural fractures and numerical solution of bottom hole pressure of horizontal wells after multi-stage fracturing were obtained. Second, approaches for optimization of stage spacing, soaking time, and well spacing were proposed utilizing the dynamic analysis. Finally, the optimization method was applied to shale oil Well XC in Changqing Oilfield. Reasonable stage spacing, soaking time, and well spacing were found to be 100−125 m, 25−35 d, and 590−610 m, respectively. The research results can provide a theoretical basis for the optimization of fracturing parameters during “well fracturing–soaking–producing” of shale reservoirs in Changqing Oilfield.
The Influence of Fractures in Shale Oil Reservoirs on CO2 Huff and Puff and Its Pore Production Characteristics
LI Fengxia, WANG Haibo, ZHOU Tong, HAN Ling
2022, 50(2): 38-44.   doi: 10.11911/syztjs.2022006
[Abstract](106) [FullText HTML](77) [PDF 4057KB](28)
To study the influence of fractures from shale hydraulic fracturing on the CO2 huff and puff, low-field nuclear magnetic resonance was adopted in CO2 huff and puff experiments with shales of different permeabilities, and the influence of fractures on the CO2 huff and puff effect in reservoirs of different permeabilities was investigated. Experimental results show that fractures significantly improve the oil production rate and recovery at the initial stage of the CO2 huff and puff operations. However, the influence of fractures on the recovery gradually decreases as huff and puff continues and the permeability increases. The influence of permeability on huff and puff of fractured cores is much lower than that of unfractured cores, which indicates that fractures may reduce the influence of permeability on recovery by CO2 huff and puff. With continuing huff and puff, the increase rate in the degree of reserve recovery of crude oil from macropores contributed by fractures declines while that of crude oil from micropores increases. Despite this finding, macropores continued to be the main contributor of crude oil production. The results indicate that the quick and high production of crude oil from macropores mainly depends on volume expansion and dissolved gas drive. In contrast, the slow and low production of crude oil from micropores is primarily brought by extraction and mass transfer. The results of this study have provided a theoretical basis for evaluating the characteristics of oil production from fractured reservoirs and improving production performance.
A Cementing Technology for Horizontal Shale Oil Wells in Shahejie Formation of Shengli Oilfield
HE Licheng
2022, 50(2): 45-50.   doi: 10.11911/syztjs.2022062
[Abstract](94) [FullText HTML](34) [PDF 1592KB](38)
The cementing of horizontal shale oil wells in Shahejie Formation of Shengli Oilfield faces some technical challenges, such as the difficulties in the casing centering and safe casing running, high performance requirements for cement slurry, and hard displacement of oil-base drilling fluids. In light of these, the amphiphilic flushing spacer system was developed , the fiber expanding and anti-channeling plastic latex cement slurry system were optimized. On this basis, a cementing technology was formed preliminarily for horizontal shale oil wells in Shahejie Formation of Shengli Oilfield by combining cementing equipments and measures including an integral elastic casing centralizer, an eccentric guide shoe, floating displacement, and annulus pressurization, etc. The cementing technology was tested on site in a preliminary prospecting well YYP1, with a normal cementing operation completed. The results of acoustic amplitude logging showed that the cementing quality of the first interface was quite high, and that of the second interface was qualified. As indicated by the research and tests, the proposed cementing technology can tackle technological problems in cementing for long horizontal sections of horizontal shale oil wells in Shahejie Formation of Shengli Oilfield and enhance cementing quality. It meets the requirements of large-scale volumetric fracturing for the cementing quality of cement sheaths and can be promoted and applied in the development of shale oil.
Drilling & Completion
Optimization and Application of Efficient Drilling Technologies for Large-Scale Well Cluster Fields in Dagang Oilfield
WANG Guona, ZHANG Haijun, SUN Jingtao, ZHANG Wei, QU Dazi, HAO Chen
2022, 50(2): 51-57.   doi: 10.11911/syztjs.2021116
[Abstract](134) [FullText HTML](63) [PDF 1807KB](45)
The development of large-scale well cluster fields in Dagang Oilfield encounters problems such as the high risk of collision between wells, difficulties in trajectory optimization and drilling acceleration, etc. According to the idea of integrating geology and engineering, the key technologies involved were studied, including well pattern deployment, wellbore trajectory and anti-collision design, casing program, and supporting drilling acceleration tools. This paper established the wellhead-target matching relationship, the priority sequence of profile type design, the V-shaped design rule for kick-off points, the casing program, and the acceleration process template of one-trip drilling. In this way, efficient drilling technologies were developed for the large-scale well cluster fields in Dagang Oilfield, and were applied to the Dagang Oilfield. The large-scale well cluster field Gangxi No.2 is the largest among the onshore well cluster fields in Dagang Oilfield. In this well cluster field, safe and scaled development of 56 wells were achieved, with a cost saving of CNY 12 million in aspects such as land expropriations for well sites and drilling relocation, and an average single-well drilling cycle of 4.42 d, and rate of penetration (ROP) of 48.64 m/h. The research and applications showed that the developed technologies displayed outstanding performance in raising the utilization rate of well sites, shortening the drilling cycle, increasing ROP, and lowering the costs. The results can provide technical support for the profitable development of Dagang Oilfield.
Key Drilling Technologies for Complex Fracture-Cavity Formation in Jingyan-Qianwei Area
WANG Wengang, HU Daliang, OU Biao, FANG Zhou, LIU Lei
2022, 50(2): 58-63.   doi: 10.11911/syztjs.2021100
[Abstract](110) [FullText HTML](44) [PDF 1710KB](35)
The Jingyan-Qianwei Area, characterized by complex geological conditions and developed fractures and karst caves, has technical difficulties such as wellbore instability, lost circulation, and drill pipe sticking. In order to solve the problems, the formation three-pressure profiles and the development of karst caves in the area were comprehensively considered to optimize the casing program. According to the geological characteristics of continental formations, an anti-collapse drilling fluid with potassium-based polymers was used to prevent the mudstone from hydration swelling and keep wellbore stability. Based on the types of lost circulation that occurred during drilling, three plugging methods were developed, namely plugging fracture-induced lost circulation with the conventional bridge plugging slurry, resolving severe lost circulation with multi-functional and pressure-bearing consolidation plugging slurry, and handling complicated situations such as multiple loss formations and upper blowout and lower loss with a packer while drilling. Through the research above, key drilling technologies for complex fracture-cavity formation in Jingyan-Qianwei Area were developed. The technologies have been tested in well PR1 in Jingyan-Qianwei Area, the results showed that the technologies can be used to solve problems such as formation collapse and severe lost circulation and keep safe drilling.
Key Technology of Optimized and Fast Slim Hole Drilling in Shenfu Block, Ordos Basin
JIA Jia, XIA Zhongyue, FENG Lei, LI Jian, WANG Yang
2022, 50(2): 64-70.   doi: 10.11911/syztjs.2021110
[Abstract](103) [FullText HTML](37) [PDF 2101KB](53)
The Shenfu Block in Ordos Basin is a tight gas-producing area. In this study, optimized and fast drilling technology for slim holes was explored to further increase the rate of penetration (ROP) and reduce the drilling cost in this block. The wellbore trajectory was optimized from "vertical–build–hold–build–hold" to "vertical–build–drop–hold" matching the formation strike, which improved the drilling efficiency. The drill bit was optimized, including the change of tooth density, adjustment of cutting tooth size and caster angle, and enhancement of stability and wear resistance. The drilling assembly, size of the drill pipe, and postive displacement motor (PDM) were optimized, and a three-dimensional (3D) vibration impactor was developed for enhancing the ROP. Additionally, the performance of the drilling fluid was improved by the introduction of a biomimetic lubricant and the optimization of the drilling fluid formula. Further, drilling parameters were also optimized. The key technology of optimized and fast slim hole drilling relying on the above measures was applied in 8 wells in Shenfu Block, realizing the one-trip drilling of the second-spud section. The ROP was increased by more than 50% and the drilling cycle was shortened by 45%. This technology provides technical support for future drilling of tight gas wells in Shenfu Block and a reference for the drilling of tight gas wells in other regions in China.
Simulation Study on Temperature Field and Rock Breaking Characteristics of the Bionic PDC Cutter in Rotating State
WU Zebing, XI Kaikai, ZHAO Haichao, HUANG Hai, ZHANG Wenchao, YANG Chenjuan
2022, 50(2): 71-77.   doi: 10.11911/syztjs.2021114
[Abstract](140) [FullText HTML](73) [PDF 4384KB](43)
Some drawbacks exist in conventional polycrystalline diamond compact (PDC) bits such as low rock breaking efficiency, bit balling, and short service life. To solve these problems, a new coupling bionic PDC cutter was designed by taking the scales of pangolins, claw toes of mole crickets, shark teeth, and scallop shells as bionic prototypes to construct bionic structures in multi-dimensions. Finite element and elastoplastic mechanics were employed to build rock breaking simulation model of bionic PDC cutters. The finite element software ABAQUS was used to study the variation law of the temperature field and rock breaking modes of bionic PDC cutters during rock breaking by temperature-displacement coupled explicit penetration contact algorithm and explicit dynamics module. The comparative simulation shows that bionic PDC cutters differed greatly with the conventional PDC cutters in the temperature transfer process during rock breaking. Bionic PDC cutters could prevent bit balling, reduce the accumulation of friction heat, avoid high-temperature thermal failure, and prolong the service life. Moreover, Bionic PDC cutters featured fast speed and thorough rock breaking. The research verifies that bionic PDC bits have good practicability and show great values in promotion and application in the field.
Study on the Influence of Salt Rock Creep on the Integrity of Cement Sheath Gas Seals
XIE Guanbao, TENG Chunming, LIU Huajie
2022, 50(2): 78-84.   doi: 10.11911/syztjs.2021113
[Abstract](264) [FullText HTML](93) [PDF 2577KB](63)
Salt rocks are prone to plastic deformation or creeping flow during drilling and cementing due to their solubility and plasticity. This may result in irregular wellbores and deformed or even collapsed casings, which influences air tightness of wellbore in salt rock interval and thereby threatening the normal production and safety of oil (gas) wells. This study aimed to provide a theoretical basis for air tightness evaluations of wellbores in salt rock intervals. For this purpose, the influences of salt rock intervals on the air tightness of the first and the second interfaces in cementing were analyzed by means of petrophysical experiments and three dimensional (3D) finite element simulations. The following results are obtained: The first interface is superior to the cement stone itself in gas sealing ability, and the ability of the second interface can be enhanced from salt rock creep. The gas sealing ability of salt rock intervals is mainly depends on the sealing ability of the second interface and cement stone itself. The gas sealing ability of salt rock intervals has a complex positive correlation with interface contact pressure. A model for quantitative evaluation of gas seal pressure at the second interface in cementing was built based on the analysis results. With this model, the air tightness of salt rock intervals in target areas can be evaluated, and it can provide reference for the cementing in similar intervals in other areas.
Simulation Study on the Key Parameters Affecting Pressure-Controlled Drainage Effect
YANG Hongwei, LI Jun, LIU Jinlu, LIU Gonghui, GAO Xu, ZHAO Xuangang
2022, 50(2): 85-91.   doi: 10.11911/syztjs.2021105
[Abstract](65) [FullText HTML](49) [PDF 2779KB](11)
Pressure-controlled drainage can effectively reduce formation pressure in a high-pressure brine layer, but the influence of some key parameters on its effect in operating process is still unclear. The characteristics of pressure-controlled drainage technology were analyzed, and its technological process was summarized. On the basis of the seepage theory of formation brine and wellbore flow theory, a mathematical model with dynamic parameters was built taking into consideration the formation pressure recovery in the shut-in period to simulate the entire process of pressure-controlled drainage. Taking Well Keshen A in Tarim Oilfield as an example, simulations were conducted and the results by simulation and measurement were analyzed. It was found that the error between them was small. The analysis of key parameters affecting the effects and cycles of water drainage showed that the shorter the shut-in time, the quicker the decline in formation pressure. When the pressure-bearing limit of throttle was raised from 5 MPa to 15 MPa, the number of times for cyclic sewage disposal could be reduced by half. However, when the formation permeability was low, the effects of the first seven operations of water drainage were remarkable, and thus the period for trial drainage was set to seven days. According to the above results, relevant improving measures were put forward to better control the key operational parameters, so as to enhance the effects of pressure-controlled drainage.
Oil & Gas Exploitation
Key Technologies for Large-Scale Acid Fracturing of Ultra-Deep Fault-Karst Carbonate Reservoirs with Ultra-High Temperature for Well S in Shunbei Oilfield
LI Xinyong, LI Xiao, ZHAO Bing, WANG Kun, GOU Bo
2022, 50(2): 92-98.   doi: 10.11911/syztjs.2021068
[Abstract](154) [FullText HTML](58) [PDF 2680KB](26)
The target formation of Well S in Shunbei Oilfield is a typical ultra-deep fault-karst carbonate reservoir. Due to the complex engineering and geological conditions and wellbore conditions, acid fracturing is confronted with great challenges. In light of above difficulties in reservoir stimulation, a set of compound acid fracturing technologies was proposed by "centralized treatment by backfilling + acid damage to reduce fracture pressure + shallow pipe string + flow rate increase by weighted fracturing fluid + pad fluid fracturing + alternative injection for high conductivity fracture + autogenous acid to connect the far fault-karst". A set of acid fracturing fluid systems was optimized for resistance to ultra-high temperature by tests, included polymer fracturing fluid at 180 ℃, weighted guar gum fracturing fluid at 160 ℃, crosslinking acid at 160 ℃, and autogenous acid. Then, an optimized large-scale acid fracturing treatment plan was made based on recommendations for working fluid scales by numerical simulation. The recommended scale of fracturing fluid was 1 000–1 200 m3 and the scale of acid fluid was 800–1 000 m3. The field test showed a significant decrease in the wellhead pressure with weighted fracturing fluid, which was 7% lower than that with polymer fracturing fluid under the same injection rate. After the large-scale acid fracturing of Well S, the test production of natural gas was 10.45 × 104 m3/d, which made a breakthrough in the exploration of the Shunbei No. 4 fault zone and provided valuable guidance for the large-scale acid fracturing design of similar reservoirs.
Application of a Gas and Water Drive Combined Characteristic Curvein Reservoirs with Gas Cap and Edge Water
YUE Baolin, WANG Shuanglong, ZHU Xiaolin, LIU Bin, CHEN Cunliang
2022, 50(2): 99-104.   doi: 10.11911/syztjs.2022014
[Abstract](113) [FullText HTML](52) [PDF 1738KB](23)
When reservoirs with gas cap and edge water enter the middle and late stages of development, challenges of gas channeling and water cut emerge, and relevant evaluations and development strategy adjustments are needed depending on evaluation results. However, the development effect of such reservoir cannot be directly evaluated by the characteristic curve of gas drive or water drive. In light of this, this paper presents a method for calculating the proportion of oil production by gas drive at different stages by combining the relations for characteristic curves of water drive and gas dive. Specifically, the relation for characteristic curve of gas dive was derived based on the steady seepage theory. The degrees of reserve recovery by gas drive and water drive in reservoirs with gas cap and edge water can be calculated using this method, and the calculation results can provide a basis for adjusting the development strategy. The calculated degree of reserve recovery by gas drive was 24.3% for the upper part of an oil group with gas cap and edge water in Well Block 3 of JZ-X Oilfield, and that by water drive was 48.4% for the lower part. Considering that the degree of reserve recovery by gas drive in the upper part was low, barrier water injection was intended to be conducted for enhancing the oil recovery of the oil group. The research indicates that the development effect of reservoirs with gas cap and edge water can be evaluated by the gas and water drive combined characteristic curve.
3D Acid Fracturing Technology in Maokou Formation of Well Jinghe 1 in Southwestern Sichuan
LIN Yongmao, MIAO Weijie, LIU Lin, LI Yongming, QIU Ling
2022, 50(2): 105-112.   doi: 10.11911/syztjs.2022009
[Abstract](98) [FullText HTML](61) [PDF 4464KB](18)
Wufeng–Longmaxi Formation is the main shale-gas production horizon in southwestern Sichuan, and good gas indication shows in Maokou Formation in logging data from wells drilled through. To make a confirmation of the gas potential of the formation, Well Jinghe 1 was drilled as a preliminary prospecting well. In light of the short effective acidizing distance and limited stimulation volume from acid fracturing in Maokou Formation of an adjacent area, the fracture and pore development characteristics of the drilled strata in Well Jinghe 1 were analyzed. A three-dimensional (3D) acid fracturing technology was researched from the aspects of full 3D fracture propagation, the acid fracturing fluid system, and supporting operation parameters. The research results show that fine sectioning by multiple packers accompanied by large-displacement can reach the stimulation effect aiming at realizing connection of fractured bodies. The three-stage alternative injection of fracturing fluid and gelled acid can increase the stimulation volume of fractured bodies and the distances of acid etched fractures. This can met the requirement of deep penetrating and non-uniform etching in the horizontal direction as well as the high production of fine sections in the vertical direction. The production of Well Jinghe 1 was 12.52×104m3/d after 3D acid fracturing, which was 38% higher than that with prepad acid fracturing. The post-fracturing fitting results indicated that fractured bodies were well connected. The successful application of 3D acid fracturing technology in Maokou Formation of Well Jinghe 1 provides a new idea for the development of gas reservoirs in Maokou Formation, Qixia Formation, and Dengying Formation in southwestern Sichuan.
Development and Performance Evaluation of a Graphene ReinforcedAluminum-Based Soluble Ball Seat
WEI Liao
2022, 50(2): 113-117.   doi: 10.11911/syztjs.2021134
[Abstract](100) [FullText HTML](70) [PDF 2483KB](20)
The re-entry of tools in horizontal wells can be negativelly affected by problems in removing the ball seat in multistage ball-drop sliding sleeves such as low drilling efficiency and incomplete removal. In order to overcome that, a graphene reinforced aluminum-based composite was developed to make soluble ball seat with sliding sleeve. By using graphene and silicon carbide ceramic particles and with powder metallurgy, a graphene reinforced aluminum-based composite was obtained. The composite possess characteristics of high strength, high hardness and self- rapid dissolution in saline environment, with yield strength of 469 MPa and surface hardness up to 170 HBW. The soluble ball seat made of graphene-reinforced aluminum-based composite could still maintain sealing and pressure-bearing capacity when eroded by sand-containing fracturing fluid with a sand ratio of 30% at a flow rate of 4 m3/min for 26 hrs, and its overall weight was only reduced by 2.1%. In addition, the ball seat could completely be dissolved in the 4% KCl solution at 90 ℃ when soaked in the solution for 32.5 hrs. The field test showed that the developed graphene reinforced aluminum-based soluble ball seat could satisfy the requirements of multistage sliding sleeve fracturing with high flow rate, high sand ratio and long operation time. After fracturing, the ball seat can dissolve by itself in downhole liquid environment to achieve a full-diameter borehole. The developed graphene reinforced aluminum-based soluble ball seat can provide clean and safe wellbore conditions for the second stimulation of the reservoir.
Quantitative Study of Vertical Sweep Degree Between Injection andProduction Wells in Thick Oil Layers
ZHANG Jing, ZHENG Bin, LI Hongying, LIU Yujuan, YAN Zhiming
2022, 50(2): 118-125.   doi: 10.11911/syztjs.2021124
[Abstract](75) [FullText HTML](43) [PDF 3566KB](15)
After a long-term scouring by injected water, the remaining oil distribution is scattered and vertical water flooding is extremely complex in reservoirs developed by water flooding, especially in the reservoirs with thick oil layers. For quantitative study of vertical sweep degree between injection and production wells in thick oil layers, motion equations of water droplets in planar and vertical directions were built based on seepage theory and giving due consideration to the oil-water two-phase flow, effective permeability, and density variation with saturation. A complete set of mathematical models describing the vertical sweep between injection and production wells in thick oil layers was developed. Taking L Oilfield as an example, according to the analysis results, the following findings could be found: a greater injection-production rate, a greater viscosity of crude oil, tighter injection-production well spacing, a lower permeability, a lower water cut, and a higher permeability change degree meant a higher vertical sweep degree of the injected water. Most affected by the thickness of the oil layers was the migration path of the water droplets instead of the sweep degree. Moreover, the injection-production rate limit in thick oil layers was 180 m3/d, and the viscosity limit of crude oil was 200 mPa·s.The limit of injection-production intensity was 3.00 m3/(d·m) when the oil layer thickness was fixed, and the limit of oil layer thickness was 30 m when the injection-production intensity was fixed. The results show that for the thick oil layers developed by water flooding, the injected water infiltrates downward due to gravity, which reduces the vertical sweep degree and recovery. In a nutshell, quantitatively evaluating the vertical sweep degree between injection and production wells in thick oil layers can provide theoretical guidance for understanding the remaining oil distribution and improving the vertical sweep degree.
Well Logging & Surface Logging
Characterization Method and Application of Electrical Imaging Logging in Conglomerate Reservoir: A Case Study in Mahu Sag of Junggar Basin
LIN Jingqi, MENG Xin, LI Qingqing, CAO Zhifeng, ZHANG Kai, MU Li
2022, 50(2): 126-131.   doi: 10.11911/syztjs.2022059
[Abstract](75) [FullText HTML](48) [PDF 2325KB](20)
Because the conglomerate reservoir in Mahu Sag of Junggar Basin has rich electrical imaging logging data, the processing method and further applications of electrical imaging logging data for conglomerate reservoirs were studied to make full use of the advantage of high-resolution electrical imaging in rock composition, heterogeneity, and reservoir structure characterization. Considering the resistivity difference of rock compositions in electrical ima-ging of conglomerate reservoirs, the cut-off value of resistivity was determined through core calibration, and the calcu-lation method for the relative content of gravel, sand, and argillaceous parts as well as the grain size analysis method of cumulative pseudo-grain-size probability curves were constructed. Through mathematical statistics, the methods for calculating the sorting coefficient, porosity, fracture porosity, and high-precision resistivity were established. Based on the understanding of the main controlling factors of conglomerate reservoirs, it was proposed that the energy storage indexes for evaluating the reservoir performance of conglomerate reservoir could be used to develop a new method for identifying reservoir fluid properties by the variance of apparent formation water resistivity spectra and reservoir indexes on the basis of electrical imaging. The energy storage indexes mainly included the rock composition factor, porosity of electrical imaging logging, heterogeneity factor, and fracture factor, etc. The research results show that the electrical imaging logging data can effectively evaluate the physical properties and oil-bearing properties of conglo-merate reservoirs, with good application effects in evaluation of field exploration. It has provided a reference for further application of electrical imaging logging data in conglomerate reservoirs.
Finite-Element Forward Modeling of Electromagnetic Response of Hydraulic Fractures in Layered Medium
WU Shiwei, LIU Dejun, ZHAO Yang, WANG Xu, FENG Xue, LI Yang
2022, 50(2): 132-138.   doi: 10.11911/syztjs.2022060
[Abstract](89) [FullText HTML](30) [PDF 3041KB](18)
For better understanding of response characteristics of electromagnetic logging instruments in fractures in multi-layer medium, based on the low-frequency electromagnetic field theory, fracture models of a single-layer medium formation and a five-layer medium formation were built with finite-element software, respectively. On this basis, forward modeling of the induced electromotive force in the receiving coil in hydraulic fractures in the layered medium was carried out. The results showed that the induced electromotive force curve changed significantly at the fracture position. When the fracture is symmetrical and the angle between the fracture and the borehole is from 25° to 90°, the smaller the angle, the more tortuous the fracture response signal, which was exactly opposite to the case when the angle was between 90° and 155°. If the fracture was asymmetrical, the larger the widening angle, the more obvious the asymmetry of fracture response signal under the condition of multi-layer medium when the widening angle was in the range of 30–150°. The research shows that a multi-layer medium has influence on the fracture response curve, and the research results provide a theoretical basis for the detection and evaluation of hydraulic fractures in horizontal wells.
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](6082) [PDF 1006KB](4064)
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](4588) [PDF 1084KB](4067)
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](6538) [PDF 1149KB](4214)
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](5089) [PDF 1211KB](4055)
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](4922) [PDF 1065KB](4539)
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](4213) [PDF 1055KB](3727)
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](4536) [PDF 1031KB](4028)
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](4121) [PDF 1085KB](4120)
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](4361) [PDF 1031KB](3674)
Research Status and Prospect of Hydraulic Oscillator Worldwide
Ming Ruiqing, Zhang Shizhong, Wang Haitao, Hong Yi, Jiang Shulong
2015, 43(5): 116-122.   doi: 10.11911/syztjs.201505020
[Abstract](6346) [FullText HTML](96) [PDF 1272KB](4310)