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Research on the Influence Factors of EM-MWD Signal Transmission in Drill String
ZHANG Hao, BI Xueliang, LIU Weikai, XU Yueqing, SONG Mingxing, SHAO Shuai
 doi: 10.11911/syztjs.2021128
[Abstract](37) [FullText HTML](13) [PDF 2010KB](0)
The drill string is an important EM-MWD signal transmission channel in existing electromagnetic measurement while drilling (EM-MWD) systems. In order to deeply understand the influence factors of EM-MWD signal transmission effect in drill string, the EM-MWD signal channel is modeled based on equivalent transmission line method, and finite element calculation is carried out using ANSYS software. Energy loss of different specifications of drill string in alternating electromagnetic field and influence of casing on EM-MWD signal transmission.It is found that the energy loss of EM-MWD signals in the drill string increases with the increase of power and frequency, and the increase is more obvious when the signal frequency exceeds 100 Hz. Different drill strings have different signal transmission effects, but when the ratio of drill string wall thickness to outer diameter is 0.08 ~ 0.20, EM-MWD signal transmission effect is better. Casing on the drill string can shield em-MWD signals, but when EM-MWD signals are transmitted at frequencies below 50 Hz, casing has little impact. The research results further clarify the influence of the properties of the drill string on EM-MWD signal transmission, which can provide reference for the improvement and design of EM-MWD system.
Performance Evaluation and Field Application of Self-Consolidating Plugging Agents
WANG Zaiming, XU Jing, ZHANG Yixin, SHEN Yuanyuan, XU Xiaofeng, LI Xiangyin
 doi: 10.11911/syztjs.2021044
[Abstract](137) [FullText HTML](43) [PDF 1681KB](71)
In light of the low success rate of plugging by conventional compound plugging agents, self-consolidating plugging agents were studied. A fluidized coating equipment was adopted to coat the outer surface of the plugging agents with a layer of epoxy adhesive that can be consolidated at downhole temperature, so as to increase the underground plugging strength of plugging agents. By adjusting the inlet air temperature of the fluidized coating equipment at 50–100 °C, the air outlet temperature at 25–40 °C, and the rate of the spray gun at 0.5–2.0 L/h, the spray, coating, and drying could be achieved. The laboratory experiments of plugging at high temperature showed that the developed plugging agents could resist the disturbance of drilling fluids and the negative-pressure suction. By selecting the specific type of epoxy resin, the dosage of curing agent and accelerator DL-1, the downhole consolidation time of the self-consolidating plugging agents could be adjusted. At 110 °C, the plugging agents began to consolidate after 2 hrs, and the strength increased to 4.6 MPa after 15 hrs. Scanning electron microscope photographs of the plugging layers showed that the coating layers were softened and then consolidated as the temperature rose, and the materials bound tightly after consolidation. The result indicated that the self-consolidating plugging agents can greatly improve the success rate of plugging in severely fractured thief zones and provide technical supports for effective plugging.
Study on Nano Composite Cement Slurry System Suitable for Low Temperature Formation
WANG Sheng, CHEN Qiang, YUAN Xuewu, HUA Xu, CHEN Liyi
 doi: 10.11911/syztjs.2021009
[Abstract](68) [FullText HTML](60) [PDF 2299KB](48)
In order to solve the problems of borehole wall collapse and well leakage during drilling in low temperature formation, a new nano-composite cement-based grouting material system suitable for low-temperature formations has been developed. The effect of nano-Al2O3 on the performance and hydration process of low-temperature silicate-thioaluminate composite cement slurry was studied by combining macroscopic test and microscopic analysis. Through the "synergistic hydration" effect induced by mixing ordinary Portland cement with sulphoaluminate cement, together with nano-Al2O3, antifreeze agent (EG), water reducing agent (JS-1), early strength agent (TEOA), a new composite cement slurry (NAC) was developed, an integrated analysis of scanning electron microscopy, X-ray diffraction and hydration exotherm was used to observe and analyze the patterns of the low temperature hydration process of NAC. The experiment concluded, at a low temperature of –9 ℃, the nano-composite cement cement (NAC) had good initial fluidity, with a pumpable period of 57 min, and 24 h compressive strength of 6.9 MPa. Research shows that NAC has the effect of 'right angle thickening' and the performance is superior at low temperature, which can meet the performance requirements of borehole wall protection and plugging in low temperature formation drilling.
Research on Proppants Conductivity Test in Low Permeability Sandstone Reservoirs in South Sea
WU Bailie, YANG Kai, CHENG Yuxiong, LIU Shanyong, ZHANG Yan
 doi: 10.11911/syztjs.2021064
[Abstract](217) [FullText HTML](81) [PDF 7964KB](48)
In order to solve the problems of lower degree of reserve recovery and difficult to form hydraulic fractures with high conductivity in low permeability reservoir in South China Sea, the laboratory experiment was conducted, the influence of different content of clay minerals on the conductivity of hydraulic fractures was analyzed, different grain size composition was adopted. The change law of conductivity with different grain size was revealed under cyclic stress loading conditions. An experiment was designed to investigate the effect of different viscosity on the conductivity of the ceramic filling layer, and reasons for the decrease of conductivity were analyzed. The experimental results show that the clay mineral content increased from 15% to 50%, and the conductivity of the 20/40 mesh proppant decreased from 54.3% to 63.7%, the optimal combination mode was 60% (20/40 mesh)+20% (30/50 mesh)+20% (40/70 mesh). The final conductivity was 116.7 D·cm and the conductivity decreased by 43.9%. When the viscosity of the breaking gel is 1 mPa·s, 10 mPa·s and 20 mPa·s, the conductivity decreases by 69.8%, 73.2% and 76.5%, respectively. The study indicate that the increase of clay minerals, the conductivity of the proppant decreases gradually, and the crushing of the proppant is mainly due to the compression between particles rather than the interaction with the reservoir. The higher the proportion of large grain size proppant, the greater the conductivity is. With the increase of close pressure, the decrease of permeability result in the loss of conductivity. The higher the viscosity is, the damage degree of the conductivity is greater. It is suggested that the fracturing fluid with lower viscosity or the clean fluids should be selected. The outcomes provide important data and theoretical basis for offshore fracturing design optimization and field treatment.
Key Technologies for Deep Horizontal Well Drilling of Shale Gas in Luzhou of Sichuan Basin
WANG Jianlong, YU Zhiqiang, YUAN Zhuo, FENG Guanxiong, LIU He, GUO Yunpeng
 doi: 10.11911/syztjs.2021062
[Abstract](42) [FullText HTML](20) [PDF 1703KB](17)
The drilling of deep shale gas horizontal wells in Luzhou block of Sichuan Basin has been chanllenged by long drilling cycle, low rate of penetration (ROP), high drilling tool vibration, poor drillability of special lithological formations, horizontal wellbore instability, high formation temperature, and high friction torque and sticking risk etc.. To solve these problems and to ensure operation safety and increase cost-efficiency, technological research was carried out on casing program design of horizontal wells, wellbore trajectory control and optimization of horizontal sections. As a result, the optimal parameters of the radical drilling method were recommended, and shock absorption, speed-up, and high efficient rock breaking technologies for special lithological formations were preferentially adopted. In addition, drilling fluid system and performance parameters were recommended based on pilot tests of ground cooling equipment. In this way, key drilling technologies with high operation safety and efficiency were formed for the deep shale gas horizontal wells in Luzhou block. Through the application of the key technologies in four wells in Luzhou block, the experimental results show that the drilling cycle was redcued by 14.5% and no downhole failure was reported for average well depth of 5,601.00 m and the horizontal section length of 1,884.00 m. So these technologies can meet the requirement of safe and efficient drilling as well as wide application scope in Luzhou.
Research on the Lateral Vibration Characteristics of Bottom Hole Assembly with Rotary Steering Tool
DI Qinfeng, RUI Zixiang, ZHOU Xing, FENG Dajun, WANG Wenchang, CHEN Feng
 doi: 10.11911/syztjs.2021059
[Abstract](52) [FullText HTML](39) [PDF 2999KB](35)
In order to improve the wellbore trajectory control effect and operation safety of rotary steerable tool, it is necessary to study the lateral vibration characteristics of bottom hole assembly with rotary steerable tool (RSBHA). Statically push-the-bit rotary steerable tool provides different steerable forces and wellbore trajectory control by controlling the driving pressures of the three pads. It can be equivalent to an eccentric stabilizer with known eccentricity and orientation. Firstly, a three-dimensional small deflection statics model of the RSBHA is established, and the spatial configuration of the RSBHA can determined based on the weighted margin method under the weight on bit and borehole wall constraints, and the location of the upper tangential point between the drill collar and borehole wall is obtained. Then the part between the above tangent point and the drill bit is taken as the effective length of the transverse vibration analysis, and the finite element model of the transverse vibration analysis is established. The transverse vibration response of the RSBHA is solved by using the mode superposition method, and the influence of working parameters and structural parameters on its lateral vibration is analyzed. For the RSBHA given in the case study, when the rotating speed is about 138.0 r/min, the dynamic displacement of RSBHA given in this paper is larger in the four positions (the distance from the bit is about 8.2 m, 18.1 m, 24.6 m, and 31.6 m, respectively). The weight on bit has a little effect on maximum bending stress of RSBHA, but eccentricity and eccentricity azimuth have great influence on the lateral vibration characteristics. For some value of eccentricity and eccentricity azimuth, the maximum bending stress of RSBHA increases significantly. The results show that the structural parameters and working parameters have a great influence on the lateral vibration, so it is necessary to optimize the design of the RSBHA to ensure the steering effect and operation safety of the rotary steering tool.
Research on Low Shear Rheological Properties of Annulus Drilling Fluid For Cementing in Kuqa Piedmont
LAN Kunxiang, ZHANG Xingguo, AI Zhengqing, YUAN Zhongtao, XU liqun, LIU Zhongfei
 doi: 10.11911/syztjs.2021058
[Abstract](53) [FullText HTML](26) [PDF 3302KB](16)
Aiming at the frequent leakage of cementing casing in the fourth and fifth spuds of ultra deep natural gas wells in Kuqa Piedmont structural belt, Tarim Basin, the actual shear rate of annulus drilling fluid during casing running is analyzed. According to the he Ba rheological model, the test data at full shear rate (1.70–1021.40 s–1) and low shear rate (1.70–340.50 s–1) are used, The total shear and low shear rheological parameters of oil-based drilling fluid are fitted respectively, and the difference of exciting pressure under total shear and low shear rate is analyzed. It is found that the actual drilling fluid shear rate is much lower than the high value of conventional total shear rate of 1021.40 s–1; Under full shear and low shear rate, the rheological parameters vary greatly with temperature and pressure; The casing activation pressure at full shear rate is less than that at low shear rate. With the increase of well depth, the difference between full shear and low shear rate is greater. The results show that for natural gas wells with narrow safety pressure window, the test data should be selected to fit the corresponding rheological parameters according to the actual low shear rate range of drilling fluid, and on this basis, the casing running speed should be reasonably designed according to the allowable casing running exciting pressure, so as to reduce the leakage during casing running.
Key Drilling Technologies for Ultra-Shallow Horizontal Wells in Jihua-1 Fault Block of Jilantai Oilfield
TAN Tianyu, QIU Aimin, TANG Jihua, LI Hao, XI Jia'nan, HUO Lifen
 doi: 10.11911/syztjs.2021038
[Abstract](150) [FullText HTML](65) [PDF 1488KB](58)
During the drilling of ultra-shallow horizontal wells in the Jihua-1 fault block of Jilantai Oilfield, some problems were encountered due to the soft Cretaceous strata in the upper part and the high hardness, poor drillability, and strong heterogeneity of the metamorphic strata in the lower part. In these wells, the build-up rate can not be predicted with certainty; the drilling cycle is long; the horizontal section of the hard strata is difficult to extend; the later completion casings are hard run safely. For the problems in this block, the drilling technologies for ultra-shallow horizontal wells were studied. Considering the geological characteristics of this region, the rock mechanics parameters of gneiss were simulated and the casing program and hole trajectory were optimized. A customized PDC bit was designed and the bottom hole assembly and speed-up tools were optimized. In addition, supporting technologies such as running float casing and using environmentally friendly low-solid drilling fluid which would effectively protect the were integrated. Thus, key drilling technologies were formed for ultra-shallow horizontal wells in the Jihua-1 fault block of Jilantai Oilfield. They were applied to four wells in the field and no downhole complexity occurred, suggesting good well completion results. These technologies provide technical support for the horizontal well development in this block.
The Research and Field Test of Life-Long Water Control Completion Technology in the Offshore Oilfield
GUO Yi, GAO Xiaofei, YI Huian, DAI Ling, XU Liqian, LIU Jia
 doi: 10.11911/syztjs.2021120
[Abstract](23) [FullText HTML](12) [PDF 2042KB](1)
In order to solve the problem of bottom water rapid coning in horizontal well development of sandstone bottom water reservoir in Offshore oilfield. Based on the analysis of the advantages and disadvantages of ICD and AICD water control completion technology. Life-long water control completion technology is studied. The life-long water control completion technology combines the advantages of ICD and AICD water control completion technology. In the initial stage, the high permeability section is suppressed to balance the liquid supply profile in the horizontal section of horizontal well. At later stages, it can automatically control liquid to constrain the high water section, which can slow down the water cut increase. Well W1 in H reservoir of X oilfield is the application of life-long water control completion technology well By comparing with production well in the same reservoir. The analysis shows that the life-long water control completion technology can restrain the rise of water cut in the process of horizontal well development, which is worthy of expanding the scale test. At the same time, it can provide reference for the development of similar offshore reservoirs.
Research on Productivity Prediction Method of Sandstone Reservoir Based on Logging Permeability Synthesis Technology
WANG Qinghui, ZHU Min, FENG Jin, GUAN Yao, HOU Boheng
 doi: 10.11911/syztjs.2021122
[Abstract](50) [FullText HTML](34) [PDF 2038KB](2)
Using conventional logging data to accurately calculate drill stem test (DST) permeability can greatly improve the productivity prediction accuracy of offshore heterogeneous sandstone reservoir. Therefore, considering the influence of macro sedimentary diagenesis and micro pore structure on reservoir permeability in Huizhou sag, the logging interpretation models of absolute permeability of different reservoir types are established. Analysis results show that the contribution of reservoirs with different permeability levels in perforated intervals to productivity is obviously different. The synthetic logging permeability is obtained by weighted summation of reservoir permeability at different levels, and the weight coefficient is constrained to highlight the contribution of advantageous reservoirs to productivity. Finally, the regression fitting equation of DST test permeability is established, the optimal solution of DST test permeability equations is obtained by continuous iteration of differential evolution algorithm. This technology is used to predict the productivity of 72 oil layers in Huizhou Depression. For 48 oil layers with productivity greater than 100 m3/d, the proportion of prediction relative error less than 30% is 90%, and for 24 oil layers with productivity between 10-100 m3/d, the proportion of relative error less than 50% is 79%. The productivity prediction method based on new permeability synthesis technology can provide effective guidance for offshore field testing and greatly reduce the cost of exploration.
Influence of Salt Rock Creep on Integrity of Cement Sheath Gas Seal
XIE Guanbao, TENG Chunming, LIU Huajie
 doi: 10.11911/syztjs.2021113
[Abstract](46) [FullText HTML](20) [PDF 2332KB](5)
Salt rock is soluble and plastic. Plastic deformation or creeping flow is easy to occur in the process of drilling and cementing, which leads to irregular shape of wellbore, deformation or collapse of casing, and affects the wellbore air tightness in salt rock section, thus affecting the normal production and safety of oil (gas) wells. In order to provide a theoretical basis for the evaluation of wellbore air tightness in salt rock formation, based on petrophysical experiments and three-dimensional finite element method, the influence of the first and second interfaces of cementing in salt rock formation on wellbore air tightness was analyzed. The results show that the gas sealing ability of the first interface is stronger than that of the cement paste itself, and the salt rock creep can enhance the gas sealing ability of the second interface; the gas sealing ability of the salt rock mainly depends on the gas sealing ability of the second interface and the cement paste itself; the gas sealing ability of the salt rock has a complex positive correlation with the contact pressure of the interface; the second boundary is obtained The quantitative evaluation model of gas seal pressure is established. The quantitative evaluation model of gas seal pressure at the second interface of cementing can provide practical guidance for the evaluation of salt rock formation air tightness in the target area, and also has reference value for similar formations in other areas.
Optimal Selection of Magnetic Ranging Tools for Relief Well Engineering Based on the Measurement Error Calculations
YU Ruifeng, DIAO Binbin, GAO Deli
 doi: 10.11911/syztjs.2021129
[Abstract](49) [FullText HTML](24) [PDF 1971KB](1)
In order to select a magnetic ranging tool with higher measurement accuracy and lower operational risk under the premise of ensuring that the accident well can be detected, the relative distance measurement errors was calculated. As the "trapezoidal" error model could not be coupled with the wellbore trajectory uncertainty, through the covariance propagation rate, the measurement error model of the magnetic ranging tool was established. Coupling the measurement error of the magnetic ranging tool with the wellbore trajectory uncertainty to obtain the total covariance matrix in the working plane of the magnetic ranging tool. The error ellipse determined by the total covariance matrix and the optimal method of the relief well magnetic ranging tool were given. From the example it could be determined that when the relative distance from the target well to the relief well is 7.41 m, the semi-axis lengths of the error ellipse are 1.26 m and 0.33 m. When the relative distance between the two wells is 6.68 m, only the Wellspot tool can be used; When the relative distance between the two wells is 5.21 m and 2.07 m, the RGRI tool is recommended. The research results show that after ranging operation, as the relief well continues to drill, the decreasing trend of the relative distance between the two wells is greater than the increasing trend of the relative distance measurement error between the two wells. When the range of the magnetic ranging tool fully covers ellipse of the relative distance measurement error between the two wells, the magnetic ranging tool with a smaller range but higher accuracy can be used.
Drilling Technique of Zhong Ping 1 well for Deep Shale Gas Horizontal Wells in the ordos basin
SHI Chongdong, WANG Wanqing, SHI Peiming, YANG Yong
 doi: 10.11911/syztjs.2021007
[Abstract](124) [FullText HTML](32) [PDF 1600KB](69)
In order to find out the potential of hydrocarbon generation and accumulation in the mud carbonate rocks of Wulalike Formation in the west of Ordos Basin, the exploration effect of unconventional resources will be improved in the area. Well Zhongping 1 is the first horizontal well of marine sedimentary shale gas deployed in Changqing Oilfield. The "double stage PDC + single bend screw" sidetracking technology was adopted to improve the sidetracking efficiency of large borehole; the "multi particle bridge plug + fiber cement" plugging technology was optimized, high-performance nano plugging high-performance water-based drilling fluid system, and the application of power drive orbit with personalized PDC bit in horizontal section. The successful exploration of zhongping1 well is estimated to be 11.65×104 m3/d, and the daily gas production is stable at (15–20)×104 m3, the successful test production of this well marks a major breakthrough in the exploration of the first horizontal well of marine shale gas in the north of China, it is of far-reaching significance to realize the orderly succession of resources.
2021, 49(5): 0-0.  
[Abstract](0) [FullText HTML](0) [PDF 3465KB](0)
2021, 49(5): 1-2.  
[Abstract](0) [FullText HTML](0) [PDF 368KB](0)
Expert Viewpoint
Development Situation and Countermeasures of the Oil and Gas Industry Facing the Challenge of Carbon Neutrality
WANG Minsheng, YAO Yunfei
2021, 49(5): 1-6.   doi: 10.11911/syztjs.2021070
[Abstract](185) [FullText HTML](167) [PDF 1835KB](84)
To fight against climate change, many countries have clearly put forward the schedule for peak carbon emission and carbon neutrality. Low-carbon economic development has turned into an irreversible trend, and low carbon has become the target of energy structure transformation. Accordingly, it is projected that the proportion of demand for fossil energy will drop sharply, which will create severe challenges for the development of the oil and gas industry. For these reasons, analyses were made on the low-carbon transformation characteristics of economy and energy under the background of carbon neutrality and the influence of carbon neutrality on the development of the oil and gas industry. Then, the main countermeasures taken by oil companies and oil service companies for carbon neutrality were introduced, including formulating green and low-carbon development strategies, accelerating the development of low-carbon energy businesses, boosting the research and applications of low-carbon technologies, increasing investment in the field of new energy, accelerating the low-carbon development in petroleum engineering, and planning the low-carbon energy service business. Finally, suggestions were put forward for the development of the oil and gas industry in China, such as quality upgrading, orderly low-carbon transformation of energy structure, acceleration of innovating low-carbon technologies, and the promotion of transformation and development in the oil and gas industry. This study provides guidance for China’s oil and gas enterprises to promote a coordinated development between new energy and the oil and gas business, and to facilitate green and low-carbon transformation and development while ensuring a safe oil and gas supply.
Drilling & Completion
Research Method and Practice of Artificial Intelligence Drilling Technology
YANG Chuanshu, LI Changsheng, SUN Xudong, HUANG Liming, ZHANG Haolin
2021, 49(5): 7-13.   doi: 10.11911/syztjs.2020136
[Abstract](158) [FullText HTML](113) [PDF 1789KB](106)
With the rapid development of artificial intelligence (AI) technology, it has made remarkable breakthroughs in many fields. However, the application of AI in drilling engineering is still in the primary stage. In order to promote the application of AI technology in drilling, based on a brief description of the research situation of its application in drilling engineering, a “three-wheels drive” methodology for the specific application of AI technology in drilling area was proposed. Then, business application scenarios and AI technology tools suitable for the research of AI in drilling engineering were analyzed. After putting forward a method of evaluating and optimizing projects based on the methodology with examples, the research process of AI application in drilling was illustrated by the real-time diagnosis of complex downhole failures. Finally, the shortcomings were identified and suggestions were given for the application of AI in drilling engineering, so as to promote the development of AI drilling technology.
Drilling Technologies for Horizontal Wells with Ultra-Long Horizontal Section and Slim Hole in Changqing Oilfield
WANG Zhongliang, ZHOU Yang, WEN Xiaofeng, LONG Bin, DING Fan, CHEN Shaowei
2021, 49(5): 14-18.   doi: 10.11911/syztjs.2021060
[Abstract](82) [FullText HTML](27) [PDF 1820KB](54)
Technical issues such as difficult wellbore trajectory control, low rate of drilling in formation, low ROP (rate of penetration), wellbore collapse, and circulation loss are easily encountered in the drilling of horizontal wells with ultra-long horizontal section and slim hole in Changqing Oilfield. In light of this, difficulties in drilling technologies were analyzed in this study and some key technologies were investigated, including intelligent wellbore trajectory control based on rotary steering, near-bit azimuthal gamma imaging, and engineering parameter monitoring. Moreover, bit selection was optimized and the application of sealing water-base drilling fluid by a formed nanometer film was studied. As a result, drilling technologies for horizontal wells with ultra-long horizontal section and slim hole in Changqing Oilfield were developed, which can enable accurate wellbore trajectory control, drilling ratio increase and ROP enhancement, and can ensure downhole safety. The rotary steering technology and related supporting technologies were applied to Well Tao XX in Changqing Oilfield, and drilling was completed safely and efficiently in a 4 466 m horizontal section at a depth of 8 008 m, with the drilling ratio of 96.6%. This created a new drilling record as the deepest well in Changqing Oilfield and the longest horizontal section on land in the Asia-Pacific region. Considering the good field application effect, the drilling technologies for horizontal wells with ultra-long horizontal section and slim hole in Changqing Oilfield are worthy of wide application.
Key Drilling Technologies in Extended-Reach Well M with Ultra-High HD/VD Ratio in the South China Sea
ZHANG Qiang, QIN Shili, RAO Zhihua, TIAN Bo, ZUO Kun
2021, 49(5): 19-25.   doi: 10.11911/syztjs.2021045
[Abstract](141) [FullText HTML](51) [PDF 2256KB](57)
In order to develop marginal oil reservoirs in an oil field in the eastern South China Sea, an extended reach Well M with a HD/VD (horizontal displacement to vertical depth) ratio of up to 4.90 was designed. During the drilling process, technical problems were encountered, such as shallow reservoir buried depth, long tangent open-hole section, narrow safe density window, difficult borehole cleaning, and strong casing-running friction resistance, etc. The drilling operation was completed owing to research and application of technologies including borehole trajectory control and casing program optimization, ECD (equivalent circulating density) control of drilling fluids in the wellbore, and safe and efficient casing-running technology. The application results showed that the borehole wall stability was greatly enhanced by the five-section casing program. The ECD change rate of the bottomhole was reduced to less than 1.9% by the continuous circulating valve system and cuttings bed destroyers. The ϕ244.5 mm casing was run to the designed depth of 4 200.00 m via the floating casing-running technology, and the ϕ177.8 mm liner was run to the depth of 5 772.00 m by the hollowed-out rotating liner-running technology. The application of the key drilling technologies of extended-reach wells with ultra-high HD/VD ratio in Well M sets a new record for China National Offshore Oil Corporation in the drilling of such wells, and provides valuable experience for the subsequent development of similar extended-reach wells.
Key Technologies for ROP Improvement in Exploratory Well Yangliu-1
ZHAO Runqi
2021, 49(5): 26-30.   doi: 10.11911/syztjs.2021095
[Abstract](73) [FullText HTML](58) [PDF 1631KB](52)
Well Yangliu-1 is an exploratory well in the surrounding blocks of Puguang Gas Field, with a design well depth of 5 850.00 m. Problems such as interlaced soft and hard continental strata, large dip angles, strong abrasiveness of the Xujiahe Formation, fractured strata were encountered, leading to difficulties in improving the ROP(rate of penetration), hard quality control of the casing program, and serious lost circulation during the drilling process. According to the lithological characteristics of strata in the well area, the air/foam drilling technology was selected to improve the ROP of upper continental strata; the PDM(positive displacement motor) + compound bit technology was employed to improve the ROP in the highly abrasive strata of the Xujiahe Formation; the pre-bending dynamic inclining prevention and fast drilling technology was adopted to enhance casing program quality; the lost circulation prevention and control technology was applied in fractured strata for a higher success rate of lost circulation control. As a result, the well was successfully drilled to the depth of 5 890.00 m, with an average ROP of 2.77 m/h, which was greatly enhanced compared with that of adjoining wells. This process had no serious downhole failures, which reduced the bit usage, shortened the time for lost circulation control, and thus achieved good economic benefits. The drilling goal has been achieved in Well Yangliu-1, which enriches the geological data of this block and provides ROP improvement experience for the drilling in this block in the future.
Technical Research and Application of Oil Base Drilling Fluid with Strong Plugging Property in Changning Block
WANG Zhiyuan, HUANG Weian, FAN Yu, LI Xiaojie, WANG Xudong, HUANG Shengming
2021, 49(5): 31-38.   doi: 10.11911/syztjs.2021039
[Abstract](114) [FullText HTML](46) [PDF 2501KB](55)
It is crucial for drilling the horizontal sections of horizontal wells in Changing Block to uncover the reasons for borehole instability in Longmaxi and Wufeng fromations and put forward the countermeasures of drilling fluid technology to strengthen the borehole stability. Based on X-ray diffraction, scanning electron microscopy, shale swelling, and rolling dispersion tests, the mechanism for the borehole instability of complex strata was revealed and a coordinative borehole stability method was proposed, i.e., "strengthening plugging of micropores, inhibition of filtrate invasion, and retardation of pressure transfer". With the test devices such as sand-bed filtration testers, high-temperature and high-pressure filtration simulators, and microporous membranes, the treatment agent of oil base drilling fluid in Changning Block, which was dominated by plugging agents, was selected. And a drilling fluid system with strong plugging property, which was suitable for Changning Block, was developed. The system had a temperature resistance of 135 ℃, salt resistance of 10%, calcium resistance of 1%, poor-soil contamination resistance of 8%, bearing capacity of 5 MPa for 400 μm fractures, and filtration loss of 0 for both 0.22 μm and 0.45 μm microporous membranes. Its plugging effect was significant, and its comprehensive performance was better than that of ordinary drilling fluid. The drilling fluid was applied to more than 10 wells in Changning Block and borehole instability was not encountered in the horizontal sections of Longmaxi and Wufeng formations. In comparison with the drilled wells applied with the conventional drilling fluid technology in the same block, the hole diameter enlargement rate of complex formations was reduced by 10.82% on average, and the construction cycle was shortened by 4.5 days on average. The research results demonstrated that the oil base drilling fluid technology with strong plugging property can effectively solve the borehole instability problem in the horizontal sections of Longmaxi and Wufeng formations in Changning Block, and it is worthy of promotion and application.
Study and Field Test of Drilling Fluid with Constant Rheology at High Temperature in West Yueman Block, Tarim Oilfield
SHU Yiyong, SUN Jun, ZENG Dong, XU Sixu, ZHOU Huaan, XI Yunfei
2021, 49(5): 39-45.   doi: 10.11911/syztjs.2021037
[Abstract](127) [FullText HTML](82) [PDF 1518KB](59)
Safe density window of drilling fluids in the deep formations of the West Yueman Block in Tarim Oilfield is narrow, and as a result, downhole complications such as lost circulation, well collapse, drill string sticking, and salt water contamination are frequently encountered. Some drawbacks exist in available drilling fluids including thickening at high temperature and a weak resistance to pollution by CO32–/ HCO3 and poor quality soil. In this paper, a drilling fluid with constant rheology at high temperature was studied, with a high-temperature-resistant polymer fluid loss additive (APS220) and a new high-temperature stabilizer (HTS220) as the base. The basic formula was determined on the basis of the performance analysis of the main agents. Laboratory tests were performed to evaluate the constant rheology at high temperature and the resistance to CO32– / HCO3 and sodium bentonite pollution of the drilling fluid. The results showed that, the drilling fluid had a plastic viscosity ratio of 1.3, dynamic shear ratio of 1.5, initial shear ratio of 1.7 and final shear ratio of 1.2 at 100 °C and 180 °C. As temperatures rose, it presented a variation range of rheological parameters significantly lower than that of other commonly used drilling fluids, with the resistance to pollution by 2% CO32– / HCO3 and 10% sodium bentonite. In the field test of two wells in the West Yueman Block, the drilling fluid demonstrated stable rheological properties, with smooth drilled borehole and considerable downhole complication reduction.
Study on Rock Breaking Mechanism and Field Test of Triangular Prismatic PDC Cutters
LIU Jianhua, LING Wenxue, WANG Heng
2021, 49(5): 46-50.   doi: 10.11911/syztjs.2021040
[Abstract](75) [FullText HTML](32) [PDF 2328KB](13)
The lack of clarity over the rock breaking mechanism of triangular prismatic cutters hinders their effective applications. In view of this, the finite element method was employed to conduct a numerical simulation analysis of triangular prismatic cutters in this study with the aim of clarifying the change rules of various cutter force during rock breaking and revealing the rock breaking mechanism. The results of numerical simulation and scraping experiments suggested that triangular prismatic cutters and planar PDC (polycrystalline diamond compact) cutters demonstrated a distinct difference in the stress on the rocks during breaking. The tangential force and its fluctuation were smaller when a triangular prismatic cutter was used to break sandstone as compared with a conventional planar cutter under the same conditions. The field test of the PDC bit with the triangular prismatic cutters proved a high efficiency in rock breaking and impact resistance in strata with high abrasiveness and strong impact. This study demonstrates that breaking rocks using tension and shear, triangular prismatic cutters can make the tangential force and torque smaller and the impact resistance and abrasion resistance higher. In that way they can enhance the rock breaking efficiency and prolong the service life of bits.
The Optimization of Casing Thread Types for Horizontal Tight Oil Wells in Mahu Oilfield, Xinjiang
SHU Bozhao, ZHAO Wenlong, WANG Hang, HUANG Yongzhi, ZHANG Zhi, ZHU Xiaohua
2021, 49(5): 51-56.   doi: 10.11911/syztjs.2021041
[Abstract](155) [FullText HTML](57) [PDF 2217KB](82)
To tackle the fracture failure of casing thread joints when running casing in horizontal tight oil wells in Mahu Oilfield, Xinjiang, numerical simulations of casing thread joints and full-scale experiments on casing were conducted to compare and analyze the connection strength and fatigue life of API-LC long round thread joints and TP-G2 special thread joints during the lifting and lowering process of casing running. The results of simulations and experiments showed that the stress of TP-G2 special thread joints was significantly lower than that of the API-LC long round ones under the same tension or compression forces, and further, the fatigue life of TP-G2 special thread joints was about 6.9 times of that of API-LC long round thread joints under the same cyclic and alternating tensile-compressive load. According to our research, TP-G2 special thread joints can play a better role than API-LC long round thread joints in meeting the technical demands for casing operation in horizontal tight oil wells in Mahu Oilfield, Xinjiang and in improving operation efficiency.
Measurement of the Downhole Drill String Vibration Signal and Analysis of the Vibration Excitation Sources
CHEN Huijuan
2021, 49(5): 57-63.   doi: 10.11911/syztjs.2021011
[Abstract](243) [FullText HTML](96) [PDF 3263KB](90)
To deeply understand the downhole drill string vibrations and clearly identify the vibration excitation sources in the drilling process, the vibration signals were measured during rotary drilling of an ultra-deep well by the ESM (environmental severity measurement) storage system. According to the principle of measurement, the stick-slip and whirling vibrations of the drill string were studied. On this basis, the frequency domain and time frequency of drill string vibrations were analyzed by the fast Fourier transform and short-time Fourier transform. Then the main frequency causing drill string vibrations was determined, and the vibration excitation sources were further identified. The results demonstrated that during the stick-slip vibrations of the drill string, the triaxial acceleration changed synchronously and periodically, with a period of 10 s and a main frequency component of 0.1 Hz. When the drill string experiences whirling vibrations, the three-axis acceleration fluctuated disorderly and irregularly, and the main vibration frequency was twice the bit speed frequency, 1 to 5 times the rotary table speed frequency. The case analysis result showed that excitation sources causing the whirling mainly consisted of the interaction between the drilling bit and the formation, the friction between the stabilizer or Power-V system and the borehole wall, etc.
Research and Application of a ϕ273.1 mm Infinite Circulation Liner Hanger in Yuanba Gas Field
GUO Zhaohui, LI Zhen, LUO Hengrong
2021, 49(5): 64-69.   doi: 10.11911/syztjs.2021004
[Abstract](98) [FullText HTML](79) [PDF 1793KB](72)
Technical problems were encountered when cementing ϕ273.1 mm liners in Yuanba Gas Field, such as long open holes and liner sections and small annular gaps, further leading to difficulties in running the liner to the targeted area and measuring slurry displacement, as well as impeding the midway pump start-up. Considering geological conditions, borehole conditions, tool functions, etc., a infinite circulation liner hanger, integrating a pressure balance mechanism and embedded slips, was adopted and combined with a supporting rubber plug system. Moreover, specific measures for running the liner were introduced. Implementing the technique in 7 wells of Yuanba Gas Field eliminated the midway circular resistance and allowed liner running into the targeted area safely with a successful rate of 100%. The compound signal of rubber plugs was evident, and slurry replacement was accurate, with a bump rate of 85%. The results confirmed the remarkable performance of the infinite circulation liner hanger in cementing the ϕ273.1 mm liner in Yuanba Gas Field. This liner hanger is worthy of popularizing, for it has provided an effective way for cementing large liners with long open holes in Yuanba Gas Field.
Short Circuit Fault Test Method and Field Application of Short and Light Liners in Deep and Ultra-Deep Wells
LIU Guoxiang, ZHAO Deli, LI Zhen, KONG Bo
2021, 49(5): 70-74.   doi: 10.11911/syztjs.2021042
[Abstract](77) [FullText HTML](45) [PDF 1551KB](48)
To accurately test the short circuit of short and light liners in deep and ultra-deep wells, a test method for the circulating pressure curves of variable density slurry was proposed after analyzing conventional test methods for liner short circuits and considering actual construction conditions. The principle and control processes of variable density cyclic tests, operable test programs, and key technical points were studied. The circulating pressure of variable density slurry was highly sensitive to the changes in downhole circulation channels, shown in pressure curves as variations. The comparison between the measured and theoretical pressure curves can reveal the short circuit situation of downhole strings. Field application results prove the test method has the characteristics of strong anti-interference capability, accurate measurement results, and simple operation, which can correctly identify the short circuit of liner strings. The test method for the circulating pressure curves of variable density slurry has overcome the difficulty in testing the short and light liner short circuits in deep and ultra-deep wells, which is worthy of wide application.
Oil & Gas Exploitation
Research on Crude Oil Thickening Mechanisms during Nitrogen Injection in Fracture-Cavity Carbonate Reservoirs
LIU Zhongyun, LI Zhaomin, ZHAO Haiyang
2021, 49(5): 75-80.   doi: 10.11911/syztjs.2021015
[Abstract](101) [FullText HTML](59) [PDF 2069KB](47)
Research was conducted on the thickening mechanism of crude oil during nitrogen injection in fracture-cavity reservoirs to clarify the thickening mechanism and take corresponding countermeasures, thereby enhancing the oil recovery of nitrogen injection. In this study, simulation experiments of nitrogen injection were performed to analyze the influence on crude oil brought by nitrogen extraction, oxygen content in nitrogen, and mixed water. The experiments showed that the oxygen content in nitrogen was the major influential factor. When the oxygen content was 1%, it took only more than 2 days to exhaust the oxygen, and the viscosity reached 18 000 mPa·s, which was 6 times the initial viscosity. When the oxygen content increased to 5%, the viscosity continued to grow to 1 122 000 mPa·s within more than 7 days, which was 366 times the initial viscosity. Emulsification with water and nitrogen extraction resulted in the same effect on viscosity: the viscosity increased 1–3 times. The results demonstrate improving the purity of injected nitrogen is the most effective way to prevent crude oil thickening of fracture-cavity reservoirs during nitrogen injection in Tahe Oilfield. It has provided a theoretical basis for solving the problem of crude oil thickening brought by nitrogen injection in fracture-cavity carbonate reservoirs.
Oil Recovery Enhancement by Composite Flooding Technology for Gasi N1–N21 Ultra-High-Salinity Reservoir in Qinghai Oilfield
JIA Zhiwei, CHENG Changkun, ZHU Xiuyu, PU Lantian, HAN Yu, HU Futang
2021, 49(5): 81-87.   doi: 10.11911/syztjs.2021121
[Abstract](38) [FullText HTML](21) [PDF 1971KB](2)
The salinity and the content of calcium and magnesium ions are ultra-high in the formation water of Gasi N1–N21 reservoir in Qinghai Oilfield. While using gel and surfactant composite flooding, conventional gels are prone to dehydrate and break, showing poor long-term stability. Meanwhile, conventional surfactants are easy to react with the calcium and magnesium ions in formation water to cause precipitation. In view of this, a high-salinity-resistant organogel suitable for Gasi N1–N21 reservoir was developed, which consisted of polymer (0.3%–0.4%) + crosslinking agent (0.2%–0.3%) + stabilizer (0.1%–0.2%). The initial setting time of the system was longer than 70 h at 68 ℃, and the viscosity after gelling was greater than 1.0×104 mPa·s. What's more, a high-salinity-resistant surfactant QH-1 was optimized, and the interfacial tension and oil displacement effect were evaluated, witha finding that the QH-1 solution with a mass fraction of 0.4% could enhance the oil recovery by 18.72%. The laboratory test results indicated that alternate injection of the high-salinity-resistant organogel and QH-1 could effectively curb the ineffective water circulation and improve the oil displacement efficiency in the low and medium permeability areas. Notably, the optimized “gel + QH-1” composite flooding was capable of enhancing oil recovery by more than 27.6%. The composite flooding was applied to 9 water-injection wells in Gasi N1–N21 reservoir. As a result, the average water cut of these oil wells decreased from 80% to 70%, and the oil production increased by 2.41 × 104 t. The research results show that the oil recovery enhancement by “gel + QH-1” composite flooding is effective in enhancing oil production and decreasing water cut in Gasi N1–N21 ultra-high-salinity reservoir, so it is worthy of promotion and application.
Laboratory Test Study of CO2 Responsive Enhanced Foam System
LYU Wei, LIU Xiaochun, BAI Hailong, PENG Minglan
2021, 49(5): 88-93.   doi: 10.11911/syztjs.2021119
[Abstract](35) [FullText HTML](25) [PDF 1845KB](9)
The development effect of CO2 flooding in low permeability reservoirs is affected by the gas channeling. In response to this problem, the foam comprehensive value was used as the evaluation index to establish CO2 responsive enhanced foam system by optimizing foaming agent with stirring method. The formula was 0.1% foaming agent AOS(alpha olefin sulfonate) adding 4.0% small molecule amine and water. Its viscosity, which was close to water viscosity before exposure to CO2, increased by more than 18 times after reaction with CO2. The results of performance evaluation indicated the foam comprehensive value of the proposed CO2 responsive enhanced foam system could reach more than 11 times those of conventional foam systems, with obvious shear-thinning characteristics. The rheological equation conformed to the rheological model of power-law fluids. With stronger viscoelasticity than those of conventional foam systems, the proposed foam system could also be used to plug the dominant seepage channels to inhibit the gas channeling during CO2 flooding in heterogeneous low permeability reservoirs and ultimately to enhance the oil recovery in such reservoirs. The research results showed that the CO2 responsive enhanced foam system could solve the problem of gas channeling and improve the development effect of CO2 flooding in low permeability reservoirs.
Numerical Simulation of Multiphase Flow in Fracture Networks in Shale Oil Reservoir
XIAN Yuxi, CHEN Chaofeng, FENG Meng, HAO Youzhi
2021, 49(5): 94-100.   doi: 10.11911/syztjs.2021090
[Abstract](108) [FullText HTML](55) [PDF 2204KB](57)
Models for multiphase flow in embedded fractures and multi-fracture-intersecting networks were built to accurately characterize the flow of multiphase fluid in complex fractures in shale oil reservoirs. The numerical simulation method was utilized to analyze the flow law of multiphase fluids in the multi-fracture-intersecting networks. The results show that the numerical simulation method for the multiphase flow in the fracture networks solves problems such as single fluid type characterization, large fracture scales, high requirements for meshing accuracy, and discontinuity of fluid parameters at the fracture interface. This method can be used to assess the communication scale of hydraulic and natural fracturesand the distance between them. The formation pressure calculated by the numerical simulation method can be used to characterize the pressure variation near the fracture networks of shale oil reservoirs with the production time. The numerical simulation method proposed in this paper shows high efficiency in computing, and provides a new technical approach for the evaluation of shale oil reservoirs.
Comprehensive Evaluation and Optimization of Circulating Working Fluids inthe Coaxial Borehole Heat Exchanger Closed-Loop Geothermal System
YU Chao, ZHANG Yiqun, SONG Xianzhi, WANG Gaosheng, HUANG Haochen
2021, 49(5): 101-107.   doi: 10.11911/syztjs.2021066
[Abstract](96) [FullText HTML](52) [PDF 1838KB](57)
In the CBHE(coaxial borehole heat exchangers) closed-loop geothermal system, the influences of different circulating working fluids on the heat exchange performance of the system are still unclear, and it is not possible to comprehensively evaluate the heat exchange performance with only a single factor. Regarding this problem, a three-dimensional numerical model of fluid flow and heat transfer for the CBHE closed-loop geothermal system was built with COMSOL and verified with field data. Then, four parameters, i.e., outlet temperature, heat exchange power, circulating pressure loss, and COP (coefficient of performance) were selected, and their weight coefficients were determined by the analytic hierarchy process. Finally, a model based on the fuzzy comprehensive evaluation method was built to comprehensively assess the heat exchange performance of nine working fluids. According to the results, the working fluids were classified into three grades, with CO2 scoring the highest, indicating that CO2 had the best overall heat exchange performance and was the optimal circulating working fluid. This model can be used to comprehensively evaluate the heat exchange performance of circulating working fluids, and with CO2 as the circulating working fluid, the heat exchange efficiency of the CBHE closed-loop geothermal system can be significantly improved.
Research and Field Tests of Coiled Tubing Fishing Technology for Sand-Buried Throttles
WANG Sifan, ZHANG Ankang, HU Dongfeng
2021, 49(5): 108-113.   doi: 10.11911/syztjs.2021067
[Abstract](138) [FullText HTML](94) [PDF 1828KB](62)
In order to solve the problem of gas well shutdown caused by the failure of fishing sand-buried throttles, a sand-burial identification method for throttles in gas wells was proposed on the basis of the structural principle of slip-type throttles. Then the complicated reasons for fishing sand-buried throttles were analyzed. Combining the throttle treatments in conventional steel wire fishing and coiled tubing milling fishing as well as pulling tubing strings, the technical ideas and operational processes for coiled tubing sand washing and sand-buried throttle fishing were studied. After that, tool string for sand washing and fishing were recommended, and the theoretical minimum sand washing displacement corresponding to the coiled tubing and its diameter was analyzed. Field test of 4 horizontal wells showed that the sand-buried ϕ88.9 mm throttles were fished after sand washing, with a success rate of 100%, and an average total time of less than 1.5 days. The research results show that this technology for sand washing and fishing the sand-buried throttles is reliable, with a high success rate and a high popularization value in field applications.
Well Logging & Surface Logging
A Method for Wellbore Integrity Detection in Deep Oil and Gas Wells
ZHANG Bo, LUO Fangwei, SUN Bingcai, XIE Junfeng, XU Zhixiong, LIAO Hualin
2021, 49(5): 114-120.   doi: 10.11911/syztjs.2021127
[Abstract](70) [FullText HTML](25) [PDF 1941KB](23)
Given the problems of multiple failure points and various failure types of wellbore integrity and the difficulty in locating and identifying failures in deep oil and gas wells, a method for wellbore integrity detection was proposed on the basis of available detection methods and integrated optimization of related equipment and processes. With acoustic and electromagnetic features as the core, this method could locate and identify tubing leakage, thread leakage, casing leakage, cement sheath channeling outside of the casing, leakage under liquid level, and multiple leakages. The wellbore integrity of a test well was detected by this method. Two leakage points in the production string and the leakage types were identified. The research and field tests indicate that the proposed method can accurately identify the failure types and locate the failure points of wellbore integrity in deep oil and gas wells. This study provides technological support for the construction, workover, and wellbore integrity management of deep oil and gas wells.
Optimization Design and Numerical Analysis of Flow Passage Converters in LWD Tools
YAO Xiaojiang, LU Huatao, SHANG Jie, WANG Qinghua, LI Yang
2021, 49(5): 121-126.   doi: 10.11911/syztjs.2021069
[Abstract](110) [FullText HTML](41) [PDF 1970KB](53)
Improper design of flow passage converter section in LWD ( logging while drilling) tools can cause local flow-field turbulence and result in serious local erosion of the tool, thus reducing its service life. It can also lead to large pressure loss of the tool and affect its applicability. For this reason, CFD (computational fluid dynamics) method was applied for the optimization design of a certain type of flow passage converter in an LWD tool. According to the full 3D numerical simulation and comparison of four design schemes, the main factors affecting the flow-field performance of the flow passage converter were thought to be the expansion angle and the continuity of the cross-sectional area of the internal flow passage. The optimal design has a smaller expansion angle, a more continuous cross-sectional area of the internal flow passage, a gentler decline in axial velocity, a minimum total pressure loss, and a more uniform flow velocity distribution in the flow field. The research results showed that the expansion angle and the discontinuity of the cross-sectional area of the internal flow passage were negatively associated with the uniformity of the flow field distribution in the flow passage converter and positively with the pressure loss. The difference between theoretical and experimental total pressure loss coefficients was not more than 0.076%, and the change trend was the same as the result of theoretical analysis. The research results can effectively serve as a theoretical basis for the optimization design of flow passage converters.
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](5815) [PDF 1006KB](4053)
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](4437) [PDF 1084KB](4062)
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](6384) [PDF 1149KB](4212)
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](4897) [PDF 1211KB](4042)
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](4741) [PDF 1065KB](4527)
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](4033) [PDF 1055KB](3720)
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](4350) [PDF 1031KB](4019)
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](4049) [PDF 1085KB](4110)
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](4231) [PDF 1031KB](3670)
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](3917) [PDF 1143KB](3768)