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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](17) [FullText HTML](5) [PDF 2158KB](0)
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..
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](13) [FullText HTML](5) [PDF 3757KB](5)
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.
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](16) [FullText HTML](2) [PDF 3369KB](1)
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.
“Casing in Casing” Isolation Refracturing Technology of Fuling Shale Gas Well
LIU Yaowen, MING Yue, ZHANG Xudong, BIAN Xiaobing, ZHANG Chi, WANG Haitao
 doi: 10.11911/syztjs.2022010
[Abstract](20) [FullText HTML](8) [PDF 2303KB](3)
Aiming at the problems of difficult construction and unsatisfactory stimulation effect in Fuling Shale Gas Field by using temporary plugging diversion refracturing technology, the principle and characteristics of temporary plugging diversion refracturing technology and mechanical isolation refracturing technology are compared and analyzed by investigating foreign shale gas well refracturing technology, and it is clarified that mechanical isolation can completely block the perforation holes of primary fracturing and accurately control the initiation of hydraulic fractures in repeated fracturing. In the Fuling Shale Gas Field, the "casing-in-casing" isolation refracturing technology test was carried out. The casing with an outer diameter of ϕ86 mm was inserted into the ϕ115 mm wellbore to cement the new closed wellbore. And the study formed a refracturing process for different remaining reserves distribution. The well section with high degree of initial fracturing is aimed at tapping the remaining resources between old fractures. The conductivity of the old fracture should also be restored in the section with poor effect of initial reconstruction. The application of this technology in well JYAHF increased recoverable reserves by 0.36×108 m3 and recovery factor by 4.8%. The result shows that the mechanical sealing refracturing technology of "casing in casing" has obvious stimulation effect and can provide technical support for the long-term and efficient development of shale gas fields in China.
Development Status and Future Trend Outlook of Intelligent Fracturing Technology at Home and Abroad
JIANG Tingxue, ZHOU Jun, LIAO Lulu
 doi: 10.11911/syztjs.2022065
[Abstract](43) [FullText HTML](6) [PDF 2103KB](6)
Through the investigation and analysis of a large number of relevant literature at home and abroad, artificial intelligence fracturing technology should be a relatively long time in the future research hot spot and focus. At present, relevant researches mainly focus on intelligent optimization of layer selection and fracturing parameters of fracturing well, intelligent fracturing materials and tools, intelligent fracturing risk warning and intelligent engineering control, etc., which constitute a complete technical closed loop and influence each other. Specific research methods mainly include big data, cloud computing, transfer learning and federated learning, block chain and digital twin. Then points out the development trend of intelligent fracturing in the future, including the integration of geological and engineering intelligent decision-making platform based on the distribution of the three-dimensional sweet spot, the research and development of multi-dimensional and multi-scale fractures four dimensions of intelligent monitoring model, the research of unattended system for the whole process and node of fracturing engineering. All of these have important reference and guiding significance for the future development of intelligent fracturing technology.
Simulation Research on Influencing Factors of Mechanical Vertical Drilling Tool Stabilization Platform
LI Ranran, ZHANG Kai, CHAI Lin, ZHANG Long, LIU Baolin
 doi: 10.11911/syztjs.2021106
[Abstract](28) [FullText HTML](25) [PDF 3412KB](0)
Automatic vertical drilling tools equipped with mechanical stabilization platform are one of the technical choices for anti-inclination straightening in deep geological drilling due to lack of electronic components, good temperature resistance and relatively low cost. How to further improve the accuracy of tool straightening is one of the key and difficult points in the research and development of mechanical automatic vertical drilling tools. In this thesis, aiming at the dynamic characteristics of the mechanical stabilization platform, based on the typical structure and working principle of the stabilization platform, the theoretical analysis model and Adams dynamic simulation model of the mechanical stabilization platform were established. Through theoretical calculation and simulation calculation, the influence factors of the stabilization platform performance were analyzed, the main influencing factors and their law of influential were determined. The results showed that the length of bias block and inner and outer radius, well inclination angle and dynamic friction coefficient between disc valves had great influence on the performance of stable platform. According to the analysis results, the optimum direction and recommended range of structural parameters of the mechanical stabilization platform are finally summarized, which provides a reference for the further optimum design and parameter optimization of the mechanical automatic vertical drilling tool.
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](31) [FullText HTML](21) [PDF 2158KB](1)
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.
Application of Low Cost Fracking Practice in Normal Stress Shale Reservoirs, Wulong Block
ZHOU Bocheng, XIONG Wei, LAI Jianlin, FANG Qilong
 doi: 10.11911/syztjs.2022011
[Abstract](46) [FullText HTML](13) [PDF 2213KB](5)
Normal pressure shale has low reservoir energy and always has low daily production, which makes it difficult to develop beneficially. Reducing the hydraulic fracturing cost without damaging production is of great significance to the commercial development of normal stress shale gas. Based on the evaluation of technical fracturing difficulties of normal stress shale in Wulong Block, combined with calculation of induced stress, stimulation of fracture network parameters and estimation of cost, stage/cluster spacing and treatment parameters were optimized. The most suitable fracturing materials and equipment were chosen. The low cost fracking practice was performed in well A, and formed a fracturing design for normal stress shale, including short stage spacing, sliding sleeve, low viscosity slick water, low cost sand and continuous high concentration sand paving. This fracturing design has obtained good effects in well A: the gas production was approximately identical to the well on the same platform with fracking parameters of middle stage spacing, short cluster spacing and ceramic proppant; the fracturing cost has been greatly reduced by 52.8%; and the fracturing performance sped up to 8 stages per day with the help of sliding sleeve and real-time adjustment. The successful practice of fracturing in well A provides a new approach and technical guidance for the commercial success of normal stress shale gas.
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](83) [FullText HTML](58) [PDF 1484KB](13)
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.
Balanced Off-Bottom Cement Plug Technology in Ecuador
LI Wandong, WU Yang, LAN Xiaolin
 doi: 10.11911/syztjs.2022032
[Abstract](19) [FullText HTML](9) [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](27) [FullText HTML](11) [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.
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](37) [FullText HTML](12) [PDF 2383KB](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.
Profile control and water shutoff fracturing technology of Medium and high water cut oil well in ultra low permeability reservoir
DA Yinpeng, LI Jianhui, WANG Fei, HUANG Ting, XUE Xiaojia, YU Jinzhu
 doi: 10.11911/syztjs.2022012
[Abstract](21) [FullText HTML](13) [PDF 2982KB](4)
Due to the influence of the high permeability zone, the water cut increases and the stimulation amplitude is low after conventional refracturing in Changqing Oilfield. According to the long-term injection-production development practice of typical reservoirs, based on reservoir 3D geological modeling and infill well production data, the stimulation mechanism of plugging and fracturing in medium and high water cut Wells is analyzed. The influence of different plugging fracturing parameters on the effect of repeated stimulation is studied. The re-fracturing technology idea of "pre-regulating and controlling water cut and dynamic multistage temporary plugging fracturing to improve unit yield" is put forward. Through laboratory experiments, the optimal PEG-1 gel concentration is 5%~10%, which can maintain a high level of gel strength. The optimal injection rate is 1.5 m3/min and the injection volume is 300~600 m3, which could effectively seal the high permeability zone at the depth of 40 ~ 80m. The dynamic multistage temporary plugging fracturing technology is optimized to increase the net pressure in the fracture by more than 5.0 Mpa, so that the fractured fracture could expand from the low stress zone to the high stress zone and the lateral remaining oil could be used. The field test results show that the average daily oil increase per well is 1.07 t/d and water cut decreases by 9 percentage points after the measure, which realizes the purpose of "increasing oil and controlling water" in the medium and high water cut Wells by re-fracturing . The successful application of this technology provides a new technical idea for repeated fracturing of ultra-low permeability reservoirs in similar medium-high water cut development stage.
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](42) [FullText HTML](15) [PDF 3094KB](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.
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](33) [FullText HTML](14) [PDF 2597KB](3)
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.
Cementing technology of nitrogen foam cement slurry for horizontal shale gas well in Eastern Chongqing Area
KUANG Lixin, TAO Qian
 doi: 10.11911/syztjs.2021103
[Abstract](1) [FullText HTML](1) [PDF 2117KB](0)
The research and application of mechanical foam cement slurry cementing technology with nitrogen were carried out to solve the leakage of fluid under low pressure in production casing and the annular pressure building up problems after multistage hydraulic fracturing in the horizontal well of normal pressure shale gas field in eastern of Chongqing. By optimizing cement slurry base formula, foaming agent and stabilizing agent, foam low density cement slurry system was designed and formed. The whole process equilibrium pressure and slurry column structure design of foam cement slurry were carried out based on the high pressure gas state equation. The model for calculating the density of foam cement slurry under wellbore pressure is established. The cementing technology for foamed cement is established. The slurry density ranges from 1.30g/cm3 to 1.55g/cm3. The half-decline period of the foam cement slurry system was increased to 33.8h. The formed foam cement rock has good mechanical properties. The elastic modulus is4.6GPa and the residual strain under cyclic loads is 0.21%. The whole process of balanced pressure cementing technology and the segmented gas injection foam with different low density cement slurry were adopted to satisfy the requirement of leakage prevention cementing. This type of foam cement slurry system and foam cementing technologyare used in 20 wells in normal pressure shale gas formation. All the wells are in excellent good cementing quality. No leakage of cement slurry during the cementing process and no gas channeling in annulus after fracturing operations. The research shows that the balanced pressure cementing by using the segment gas injection technology in foam cement slurry can prevent the leakage in cementing normal pressure shale formation. The foam cement sheath with good elastic property can prevent the annulus pressure building up problems after hydraulic fracturing. The technology provided in this paper is a new method to solve the leakage and annulus pressure building up problems in horizontal wells in normal pressure shale gas formation.
Preparation and field test of Binary Complex Foam Agent COG
WANG Weiheng, LU Junhua, HAN Qian
 doi: 10.11911/syztjs.2022053
[Abstract](13) [FullText HTML](7) [PDF 1788KB](0)
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.
The Research and Application of Slick-Water and Gelling-Liquid Integrated Fractring Fluid
WEI JuanMing
 doi: 10.11911/syztjs.2022063
[Abstract](6) [FullText HTML](1) [PDF 2038KB](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.
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](28) [FullText HTML](12) [PDF 1895KB](5)
Expandable profile liner(EPL) is a new technology in oil drilling and welding is one of the key processes in the application of which. The overall pressure bearing capacity of EPL is determines directly by weld quality. In this paper, the welding technology and weld expansion performance of EPL are studied. Two kinds of welding processes using in engineering such as manual welding and automatic welding have been introduced. The downhole weld expansion simulation and weld expansion performance analysis have been carried out by using methods of elastic-plastic mechanics and finite element analysis on small-size 8-shaped EPL of Ф149.2 mm, and the test and engineering application verification of EPLs have been done. The simulation analysis and test show that the maximum point of weld stress-strain is in the trough outside of pipe wall in the process of expansion. The variation law of deformation in the internal pressure progress is the same as stress-strain for weld and bellows body. The weld stress-strain is always greater than those of the bellows body. The bellows is still in the safe range when pressurized to 30 MPa. 18 MPa can be enough to meet the mechanical expansion requirements, when Ф 149.2 mm EPL is hydraulically expanded and pressed in the field application. The results show that the welds obtained by the welding process in this paper meet the field expansion requirements. The variation law of stress-strain of EPL welds obtained by simulation analysis is basically consistent with the test results, which can guide certainly for field application.
Research on Polygonal Quartz Sand Flushing Fluid for Cementing of Oil and Gas Wells and Its Field Application
HE Licheng
 doi: 10.11911/syztjs.2022064
[Abstract](32) [FullText HTML](11) [PDF 1706KB](2)
Conventional flushing fluid cannot effectively clean the filter cake on the well walls, especially the oil-bearing filter cake formed by oil-base drilling fluid on the well walls and the oil film attached to the casing walls, which seriously affects cementing quality. Therefore, according to the idea of strengthening the physical scouring effect of flushing fluid, the polygonal quartz sand particles with sharp corners and irregular shapes and the suspending agents were selected, and the polygonal quartz sand flushing fluid was prepared. The laboratory test revealed that the prepared flushing fluid featured high stability and good compatibility with cement slurry drilling fluid, and the flushing efficiency was higher than that of conventional flushing fluid by 10–30%. Then, the prepared flushing fluid was successfully applied to four wells in Shengli Oilfield, and the cementing quality was significantly improved. The research and application indicate that the prepared flushing fluid can 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 is enhanced to meet the requirements of large-scale fracturing for the cementing quality of cement sheaths.
Experimental Study on Sand Carrying in Horizontal Annulus of Supercritical CO2
SUN Xiao, WANG Haizhu, LI Yingjie, ZHENG Yong, LU Qun
 doi: 10.11911/syztjs.2021099
[Abstract](67) [FullText HTML](32) [PDF 2626KB](7)
In order to clarify the law of horizontal annular sand transport in the process of supercritical CO2 drilling for unconventional oil and gas resources, an experimental device was designed by using similarity principle. Then the effects of injection mass flow rate, sand concentration, outlet pressure and fluid temperature on sand migration velocity and sand bed height in horizontal annulus are studied experimentally. The results show that supercritical CO2 can effectively carry sand in the horizontal annulus in the form of suspension transportation under the experimental conditions. Increasing the mass flow rate will enhance the turbulence intensity in the annulus, and then improve the effect of suspended sand transportation. At higher sand concentration, sand bed is more likely to appear at the bottom of horizontal annulus, which reduces the flow area and increases the sand velocity. Under the same injection conditions, the migration speed of sand particles in the annulus decreases with the increase of outlet pressure, and the decrease is gradually reduced. In addition, increasing the fluid temperature is beneficial to reduce the accumulation of sand particles in the annulus. This study can provide a reference for parameter optimization design during supercritical CO2 drilling and production.
Research of the Development of Digital Twin Technology in Drilling Engineering
YANG Chuanshu
 doi: 10.11911/syztjs.2022068
[Abstract](17) [FullText HTML](7) [PDF 1695KB](6)
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.
Numerical study of the erosion process of natural gas hydrate using swirling jet and experimental validation
ZHANG Yiqun, HU Xiao, WU Xiaoya, Li Gensheng, Tian Shouceng, Zhao Shuai
 doi: 10.11911/syztjs.2022046
[Abstract](36) [FullText HTML](9) [PDF 4143KB](8)
In order to explore an efficient development model suitable for the characteristics of natural gas hydrate resources in the South China Sea, the erosion performance of conical jet and swirling jet on hydrate bearing sediments under submerged confining pressures were compared and analyzed in this paper. Firstly, the Lagrangian-Eulerian (ALE) fluid-solid coupling model was established by using LS-dyna software to analyze the influence of submerged confining pressure environment on the erosion efficiency of two types of jets on hydrate bearing sediments. The erosion experiments were carried out based on the self-designed visual experimental device for gas hydrate generation and jet erosion. After the secondary formation of hydrates, gypsum was injected into the erosion pit to achieve quantitative characterization of the erosion pit depth and pore size. Through comparative analysis of numerical simulation and experimental results, it is concluded that the confining pressure can increase the strength of hydrate sediments while inhibiting the jet diffusion ability, and reduce the jet erosion efficiency of hydrate sediments. Under the condition of no confining pressure and 5 MPa confining pressure, the volume of hydrate bearing sediments eroded by swirling jet is 1.8 and 1.7 times that of conical jet, respectively. The results show that 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 downhole jet erosion process of the integrated method of radial jet drilling + screen completion integrated method of natural gas hydrate(NGH)high-pressure water jet drilling, and also provides a new technical idea for the production of NGH by the solid fluidization method.
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](24) [FullText HTML](13) [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](20) [FullText HTML](3) [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.
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](35) [FullText HTML](16) [PDF 4169KB](8)
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.
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](22) [FullText HTML](6) [PDF 1867KB](9)
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](19) [FullText HTML](13) [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](38) [FullText HTML](15) [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](76) [PDF 19158KB](41)
2022, 50(2): 1-2.  
[Abstract](84) [FullText HTML](32) [PDF 367KB](35)
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](167) [FullText HTML](98) [PDF 1991KB](92)
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](123) [FullText HTML](86) [PDF 1885KB](52)
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](156) [FullText HTML](67) [PDF 1646KB](51)
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](77) [FullText HTML](29) [PDF 2516KB](20)
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](195) [FullText HTML](63) [PDF 3651KB](66)
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](98) [FullText HTML](71) [PDF 4057KB](26)
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](87) [FullText HTML](29) [PDF 1592KB](34)
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](130) [FullText HTML](60) [PDF 1807KB](44)
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](104) [FullText HTML](41) [PDF 1710KB](30)
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](99) [FullText HTML](37) [PDF 2101KB](52)
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](133) [FullText HTML](71) [PDF 4384KB](42)
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](259) [FullText HTML](93) [PDF 2577KB](62)
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](64) [FullText HTML](48) [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](147) [FullText HTML](57) [PDF 2680KB](25)
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](103) [FullText HTML](50) [PDF 1738KB](22)
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](89) [FullText HTML](54) [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](96) [FullText HTML](68) [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](73) [FullText HTML](41) [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](72) [FullText HTML](45) [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](86) [FullText HTML](29) [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](6077) [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](4586) [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](6535) [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](5081) [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](4916) [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](4208) [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](4531) [PDF 1031KB](4026)
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](4120) [PDF 1085KB](4119)
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](4359) [PDF 1031KB](3674)
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](4000) [PDF 1143KB](3772)