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2025,52(1):1-4, DOI: 10.12143/j.ztgc.2025.01.001
Abstract:
Abstract
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WANG Bohui, ZHAO Longfei, YIN Wubing, LIU Shichang, XIN Junjie, ZHU Yufeng
2025,52(1):5-16, DOI: 10.12143/j.ztgc.2025.01.002
Abstract:
Deep reservoirs with abundant oil and gas resources are difficult to exploit safely and efficiently due to complex geological conditions and engineering factors. The problems of stuck drilling， well collapse， and well leakage caused by unstable wellbore walls have led to huge losses to drilling engineering. Therefore， this paper analyzes the mechanical mechanism of unstable wellbore walls and focuses on the influence mechanism of mechanics and multi-field coupling on unstable wellbore walls. Finally， it proposes suggestions for promoting the theoretical and technical development of drilling in weak side of deep stratified formations. The study found that the development of weak side， high temperature and high pressure environment， changes in rock layer inclination， and hydration of rocks are the main factors that weaken the mechanical strength of rocks and cause instability of the wellbore walls in deep reservoirs. The mechanical strength of rocks under different inclinations is significantly different， and the weak side of stratified rocks is more likely to swell due to hydration， which requires the rational optimization of drilling engineering parameters and drilling fluid density. This paper systematically summarizes the research on the rock mechanics and related aspects， deeply understands the mechanical influence mechanism of wellbore wall stability in deep reservoirs， and provides reference for actual production and engineering practice.
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TANG Fenglin, ZHAO Rongxin, SMESHOUV H. G., LI Bo, LIU Hao, ZHOU Xin, DUAN Longchen
2025,52(1):17-24, DOI: 10.12143/j.ztgc.2025.01.003
Abstract:
Turbo drilling is a conventional drilling method in oil and gas drilling and it has been used for many years in Russia and is being studied and used in geological exploration drilling of China. However it is not enough to develop and use the small-sized turbo drill in directional drilling in China. In Russia the small-sized turbo drill （its diameter 70mm and length 650mm） has been developed and used in drilling of geological exploration holes successfully and good technical and economical results obtained. That deserves our attention.
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ZHU Zhitong, WU Chuan, WEI Hairui, SHEN Xianhong, LIAO Yuhao
2025,52(1):25-31, DOI: 10.12143/j.ztgc.2025.01.004
Abstract:
When applied to core drilling， the traditional measurement methods while drilling are limited by the blockage of the mud pulse transmission channel by the core barrel. The measurement instrument are installed behind the core drilling assembly， resulting in a large distance between the instrument and the bit， which leads to significant lag in trajectory and operating condition data， and thereforea affects the precise control of drilling process and trajectory. A near-bit measurement system while drilling for wireline coring is proposed to address this issue. The system utilizes a near-bit transmitting unit to collect operating conditions and trajectory data in real time. The collected data is transmitted via very low frequency electromagnetic waves to be stored in a receiving unit connected to the core drilling assembly’s inner tube. After core extraction， the instrument is lifted along with the core barrel for data retrieval. This paper introduces the system’s overall scheme and circuit design， moreover， experiments for short-range transmission function are carried out. The results demonstrate that the system can achieve near-bit information transmission across the core drilling assembly downhole， with a wireless transmission distance of up to 8m. These research findings can serve as a reference for researchers in the field of near-bit measurement system while drilling.
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WEI Hairui, ZHU Zhitong, WANG Jiuquan, LIU Kuo, JIA Minghao, JIA Wei, YAN Jia, SHAO Yutao, LIU Guang
2025,52(1):32-39, DOI: 10.12143/j.ztgc.2025.01.005
Abstract:
Wireline coring is a widely used technology for core drilling without tripping the drill string. However, for horizontal and deep vertical holes, process of lowering the wireline coring tools is challenging and time-consuming, in which the efficiency decreases with the hole depth. Based on hydraulic lifting principles, utilizing the power of drilling fluid circulation, using a positive circulation for core drilling and a negative circulation for hydraulic fishing, the running-in-hole and fishing system is designed based on the existed coring drill, and the H-caliber hydraulic lifting wireline coring tool is developped. The tool are tested for 3 visualized rack, 4 core drilling runs, and 2 hydraulic lifting runs in a drilling platform and experimental boreholes. As a result, the coring operation is successfully completed and the hydraulic lifting recovery of the inner tube assembly is achieved, which offers a new perspective for coring in horizontal and deep vertical holes.
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HAN Zelong, LI Xiaoyang, SHI Shanshan, WANG Yingli, ZHOU Qingquan, MA Yinlong, TIAN Yingying
2025,52(1):40-47, DOI: 10.12143/j.ztgc.2025.01.006
Abstract:
In the process of strategic mineral resources exploration and sampling， the traditional vertical hole faces some difficulties， such as high investment in a single hole and limited access to geological information， which cannot meet the needs of high efficient exploration. Therefore， a directional continuous coring technique is proposed based on wireline coring and directional drilling technology， which can efficiently and accurately obtain geological cores in underground three-dimensional space. To solve the technical difficulties of low drilling efficiency in hard rock， easily break of drilling tools and difficulty in continuous core acquisition， the effects of weight on bit （WOB）， rotation speed and deviation rate on directional coring were studied by simulation. The results show that the WOB and rotation speed are proportional to the drilling speed ，deviation rate and bend-joint stress. When the WOB is more than 30kN and the rotation speed is more than 230r/min， the deviation rate of 6°/30m can be satisfied. Based on the comprehensive consideration of drilling tool life， the preferred WOB is 25~30kN and the preferred rotation speed is 230~300r/min. The contact stress between the core and core tube becomes larger with the increase of the deviation rate， but the final contact stress will be kept within the stable range. The maximum contact stress was 514.7MPa when the deviation rate is 9°/30m， which is less than the yield strength of coring tube. The study provides theoretical support for the coordinated optimization about drilling parameters and deviation capacity of directional continuous core drilling tools.
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YANG Fang, CAO Fan, LIU Zhenxin, ZHAI Yufeng, TIAN Zhichao, WANG Luzhao
2025,52(1):48-54, DOI: 10.12143/j.ztgc.2025.01.007
Abstract:
The 3000m scientific deep drilling project （JSD hole） of the west Sichuan Jiajika Lithium Mine is located in the central and northern part of the Qinghai-Tibet Plateau， with a final drilling depth of 3211.21m and the construction period of only 232d， creating a record in the field of small-bore solid mineral exploration on the Qinghai-Tibet Plateau and a national efficiency record of the same type of drilling. This article systematically analyzes the measures to improve the drilling efficiency of JSD hole from the aspects of drilling equipment and tools， drilling technology and methods， construction organization and management. The specific measures are summarized as follows： reasonable selection of drilling equipment and tools is the foundation， specific drilling techniques and methods are the key such as wire-line coring hydraulic hammer drilling technology， environment-friendly flushing fluid technology， hole accident prevention and so on， moveover， the standardized organization and management is the guarantee. The efficient drilling measures of JSD hole can provide reference for improving the drilling efficiency of deep and extra-deep hole construction in the Qinghai-Tibet Plateau.
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TIAN Zhichao, YU Sen, ZHAI Yufeng, YANG Huaijun, LIU Zhenxin, YANG Fang, GUO Yaoxin
2025,52(1):55-62, DOI: 10.12143/j.ztgc.2025.01.008
Abstract:
The sedimentary strata has poor stability， and accidents such as shrinkage， collapse， block falling， and adsorption sticking are prone to occur. Conducting core drilling in sedimentary strata has always been a technical challenge in the drilling field. This article introduces the construction technology of core drilling in ultra thick sedimentary layers for the Zhangye geothermal core drilling project （ZC1 well） in Gansu Province. The various drilling techniques has been innovatively applied in this project， the research and application of flushing fluid systems， deep hole coring equipment， etc.， are conducted， which solved the problems of borehole instability， adsorption sticking， drilling tool failure， and low drilling efficiency due to ultra thick sedimentary layers. It has formed a continuous core drilling process system for ultra thick sedimentary layers， providing reference for the subsequent drilling constructions in the similar complex formations.
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SHEN Lina, LI Chun, ZHAO Yi, LIU Hailong, WU Haixia
2025,52(1):63-68, DOI: 10.12143/j.ztgc.2025.01.009
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Dry drilling has little impact on the environment. In the absence of cooling medium， it can effectively solve the problem of borehole coring when drilling some water or drilling fluid reacts or produces new pollution， so this method is one of the important means of exoplanets sampling. However， exoplanets object drill bits were mostly alloy drill bits， which had certain limitations for drilling into hard rock formations. Diamond drilling is a relatively advanced rotary drilling technology， which is widely used in oil and gas exploration and geological exploration， and is a powerful tool for drilling hard rock formations. In this paper， the dry drilling tests of diamond drill bits were carried out for hard granite， and the influences of drilling parameters and bit types on the thermal characteristics during the drilling process is discussed. The results show that： （1）The heating rate of PDC drill bits is lower than that of conventional diamond coring bits， which is about 1/2 of that of impregnated diamond bits； （2）PDC coring bits can be a way for the dry drilling of granite under suitable process parameters；（3）The rotary speed has a great influence on the temperature rise of diamond bits in dry drilling， and it shows a nonlinear growth trend；（4）The cooling curves of drill bits in air show an exponential downward trend. During the cooling from 300°C to 100°C， the cooling rate≥60°C/min. The research results can provide a basis for the scientific design and rational use of dry drilling bits.
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REN Jianfei, LEI Gang, LIU Xiangjun, LU Chunhua, XIONG Jian, LIANG Lixi
2025,52(1):69-78, DOI: 10.12143/j.ztgc.2025.01.010
Abstract:
Deep shale exhibits high water sensitivity and high-temperature characteristics， and the coupled effects of hydration and temperature have a significant impact on the physical and mechanical properties of shale. Using deep shale samples from the Longmaxi Formation in the Sichuan Basin as the research subject， fracture parameters， ultrasonic parameters， and mechanical parameters of the shale after immersion under different temperature conditions were obtained through experiments involving X-ray diffraction （XRD）， scanning electron microscopy （SEM）， hydration-temperature coupled immersion tests， ultrasonic testing， and laboratory mechanical compression.The experimental results reveal that， the energy of ultrasonic waves decayed with increasing immersion time under both ambient temperature （24°C） and high-temperature （120°C） conditions. The reduction in longitudinal and transverse wave velocities in the high-temperature environment was 1.41 and 1.71 times greater， respectively， than that under ambient conditions. Hydration caused changes in the fracture parameters of the shale， showing a phased behavior. The ultrasonic attenuation coefficient and hydration-induced structural damage coefficient increased rapidly in the early stages of hydration， increased gradually in the middle stages， and tended to stabilize in the late stages. The ultrasonic attenuation coefficient and hydration damage coefficient at high temperatures were 1.72 and 2.98 times higher， respectively， than that under ambient conditions. Additionally， the mechanical properties of the shale deteriorated after immersion， with compressive strength， elastic modulus， internal friction angle， and cohesion showing a staged decline. Under high-temperature conditions， the reduction in these mechanical parameters was 1.24， 1.42， 2.06， and 1.39 times greater， respectively， than that under ambient conditions. The findings of this study provide a theoretical basis for optimizing geological designs for horizontal drilling in deep shale formations and for adjusting drilling fluid densities.
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GUO Qiang, ZHANG Delong, YANG Peng, WENG Wei, WU Shuo, JIN Bo
2025,52(1):79-84, DOI: 10.12143/j.ztgc.2025.01.011
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Flexure shaft is a key component for torque transfer between the joints of ultra-short radius flexible motor units. Aiming at the failure phenomena such as fracture of flexure shaft in the drilling process of ultra-short radius flexible motor， this paper carries out mechanical modelling and design strength checking of the internal flexure shaft of the flexible motor， uses finite element simulation to carry out stress analysis on the stress state of the flexure shaft in the torque transmission process of the flexible motor， and tests the mechanical properties of the flexible motor through indoor teststo analyse the mechanical properties of flexure shafts. The results show that the root and spline contact surfaces of the flexure shaft are the stress concentration areas in torque transmission， and the fatigue life of the flexure shaft can meet the requirements of continuous downhole operation. The finite element analysis and indoor tests show that the flexure shaft can transmit torque of 500N·m， which can realise the internal torque load transmission of the flexible motor under alternating bending and torsional stresses. This provides an important theoretical basis for the drilling process of ultra-short radius flexible motors in the development of horizontal wells， and provides a new type of technical means to improve the drilling length and drilling efficiency of the horizontal section of ultra-short radius horizontal wells.
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WANG Xiaoyu, ZHENG Mingming, WU Shuang, YAN Shichun, MA Ting, TANG Chengxiang
2025,52(1):85-93, DOI: 10.12143/j.ztgc.2025.01.012
Abstract:
The South China Sea has been confirmed to be rich in oil and gas resources as well as natural gas hydrate resources. However， hydrate-bearing formations are often encountered during the drilling of oil and gas wells. Cementing is a critical step in oil and gas development. In deepwater drilling， the heat released during cement hydration can potentially induce hydrate decomposition， compromising formation stability and even affecting cementing quality. This study utilized numerical simulation methods， focusing on the hydrate-bearing formation at the SH7 site in the Shenhu area of the South China Sea GMGS-1 project. A numerical model for cementing was established to analyze the issues caused by cement slurry invasion into hydrate-bearing formations and the impact of cementing process parameters. The study found that an increase in cement hydration heat release rate significantly advanced the onset of gas and water influx， as well as increased its volume. The cementing pressure differential had a minor impact on the influx phenomenon， but it suppressed the influx when exceeding a certain threshold. Prolonging the pressure maintenance period significantly delayed the initiation of influx and reduced its volume. Therefore， it is recommended in practical engineering to use low-heat cement， extend the pressure maintenance period， and avoid excessively high cementing pressure differentials in the early stages to minimize hydrate decomposition and mitigate the occurrence of influx. This research provides a theoretical foundation for the cementing of hydrate-bearing formations， which is of great significance for enhancing the safety and efficiency of cementing operations.
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DAI Rui, MA Chuanhua, HUANG Honglin, WU Yanhui, LUO Ming, LI Wentuo, ZHANG Botao, GAO Reyu
2025,52(1):94-102, DOI: 10.12143/j.ztgc.2025.01.013
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When drilling deep fractured formation， the formation breathing effect caused by wellbore pressure fluctuation is easy to be misjudged as overflow and unnecessary killing measures are taken， which seriously affects the drilling safety. Therefore， an experimental equipment was developed to simulate the breathing effect of fractured formation. A series of experiments were carried out to analyze the effects of drilling fluid circulation pressure， fracture opening pressure and rock type on the characteristics of drilling fluid leakage and flowback. The results show that the fractured breathing effect is a reversible leakage， and the whole process of its occurrence is leakage-“quasi-steady”-flowback. With the increase of circulating pressure of drilling fluid， the maximum leakage and return amount of drilling fluid increased. With the increase of fracture opening pressure， the maximum leakage amount of drilling fluid increases， but the return amount decreases. Compared with sandstone and limestone， granite with extremely low porosity and low permeability has larger leakage and smaller return amount. The research results provide a theoretical basis for analyzing the characteristics of fractured breathing effect of deep fractured formation and adopting correct measures to distinguish other operating conditions.
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GONG Haoyu, REN Peigang, ZHANG Furong, MA Di, XIE Bingxi, FAN Haijiao
2025,52(1):103-109, DOI: 10.12143/j.ztgc.2025.01.014
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Aiming at serious leakage problems such as crack type and karst cave type， a dual liquid method is proposed for plugging. Specifically， it is a new type of plugging technology that injects two or more fluids with different properties into the wellbore at the same time， and uses the thixotropy generated by the mixed fluid to seal the lost circulation layer. In order to study the plugging performance of mixed fluid and obtain the best plugging formula， organic gel solution is used to prepare cement slurry indoors， and mixed with Bantu slurry in different proportions. The thixotropy of mixed slurry is measured by hysteresis loop method to evaluate its plugging performance. The results show that when the dosage of organic gel is 0.08% bwoc， the cement slurry prepared by organic gel solution and 0.25% Bantu slurry are mixed at a ratio of 10∶1.8， the slurry has the best plugging performance， and the compressive strength after curing can meet the requirements of on-site construction. Field application shows that the combination of cement slurry prepared with organic gel solution and bentonite slurry has good plugging effect.
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GAO Yuan, LI Xiaojiang, LIU Rengguang
2025,52(1):110-115, DOI: 10.12143/j.ztgc.2025.01.015
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Aiming at the strength of set cement with sand degradation leads to the annular seal failure at 200℃， rich silica-aluminum material with hydration activity was developed， and when the adding amount for 30% to 70% of cement ，the compressive strength of cement are stable at 200℃×20.7MPa×30d. Based on the rich silica-aluminum material as a high temperature stabilizer， selecting matching additives， the rich silica-aluminum ultra-high temperature cement slurry was developed， the API water loss is less than 50mL at 100~200℃， the thickening time can be adjustable between 150~500min， the comprehensive performance is good. Compressive strength of set cement cured for 10d， 60d， 120d， 180d under 200℃×20.7MPa are all greater than 26MPa， and high temperature strength decline was not observed. The ultrasonic strength curve shows that the strength of set cement grows steady within 600h. The SEM and XRD shows that， the rich silica-aluminum material participate in the cement hydration reaction， and eliminate the calcium hydroxide， and generate aluminum-oxide tetrahedron and silica-oxide tetrahedron inter-bonding three-dimensional network structure with good high temperature performance， and together with tobermolite calcium silicate bauxite to maintain the stability of the high temperature strength of cement stone. The cement slurry system has been applied in hot dry rock cementing for 1 well， and the cementing quality is good. As so far， the cement ring has been well sealed for 1000 days.
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WEI Daifeng, ZHANG Meng, RAN Hengqian, MA Zhipan, YUAN Wenzhen, LI Tongtong, LI Mingjie, ZHANG Yi
2025,52(1):116-121, DOI: 10.12143/j.ztgc.2025.01.016
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Comparing low altitude drilling， plateau drilling is more challenging and fraught with dangers. In plateau and cold climates， equipment modification is the primary means to complete drilling operations. This article is focused on the different issues that arise when drilling in a field on a particular high-altitude cold plateau which include low equipment power， inadequate lubrication and personnel support， in addition， the adaptation of drilling equipment to cold and plateau conditions is implemented. The number of generators will be expanded to eight units as the 30% loss in engine power and the reform requirement of other devices ，in the meantime， appropriate lubricants will be chosen concurrently to add equipment insulating devices. An apartment building with thermal insulation was constructed in the desert to address the issues of extreme cold， oxygen deprivation， and low water quality. Diffuse oxygen supply panel and oxygen supply equipment are also added， at the same time， the water was purified using a permeable water source purification system. By the above mesures， the issues of low temperature， low oxygen， and low pressure that workers and equipment encountered are resolved，which will support technical assistance for the exploration of geological resources on the plateau.
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LIU Xiaolin, GAO Jieyun, WANG Jiarui, CHEN Haowen
2025,52(1):122-129, DOI: 10.12143/j.ztgc.2025.01.017
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In deep-sea drilling， deepwater instruments’ water tightness and pressure resistance should be verified by pressure simulation testing system before launched. So deepwater pressure simulation testing system is often used. This article improves the traditional deepwater pressure simulation testing system， the improved system''s electrical control part is mainly composed of KingView and PLC. The system uses PLC as the lower computer， and through its built-in A/D module， combined with pressure sensors， it can collect pressure signals. Users can set parameters and preset programs， and control the on-off of the pump and the valves through digital outputs， contactors， etc. The system provides auto-manual dual-mode. By combining the PLC serial port with the Bluetooth serial port transmission module， remote device display can be achieved. KingView was developed as the upper computer， to communicate with the lower computer via serial port based on Modbus RTU protocol， develops a human-machine interaction interface through configuration programming， realizes pressurization， pressure holding， and unloading setting for the entire process of pressure simulation testing， as well as monitoring the testing process， displaying pressure curves， and reporting forms. The deepwater pressure simulation testing system has the advantages of friendly human-machine interface， intuitive simulation monitoring， complete functions， reliable performance， convenient operation， safety， and scalability.
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ZHU Disi, MENG Xianglong, WANG Shengjian, WANG Xiaoming, CHEN Zhaoming, CHI Huanpeng, ZHAO Hongbo, GAO Yongjin, LI Dayong, YUE Weimin
2025,52(1):130-138, DOI: 10.12143/j.ztgc.2025.01.018
Abstract:
Well Xinsudi-2 is an oil and gas geological survey well deployed in the Xinjiang Tarim Basin. The well was drilled to 2468.50m with an open hole section of 2009.24m. After geological assessment， it was designed to be deepen drilling to 3168m. This article takes the 500~600m well section as an example to analyze the wellbore stability. The wellbore is soaked in drilling fluid for a long time， which causes the water content of the wellbore to increase. The cohesion and internal friction angle of the mudstone and other strength indicators decrease， resulting in the wellbore not having pressure-bearing capacity， slight disturbance will cause the well wall to become unstable. The project team adopted a new anti-pollution polymer anti-collapse drilling fluid system， a drilling tool assembly with a drill-while-drilling jar to relieve stuck conditions under complex well conditions， and the target layer was drilled using low drilling pressure\low rotational speed\low-displacement parameter combination drilling and other technical methods has solved a series of complex situations caused by long open-hole sections and long time soaked formations， ensured the smooth completion of the project and achieved the geological purpose， and accumulated the experience and technology of drilling long open hole and long-immersion formations.
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HUO Fengsen, XI Yizhen, JING Jing, ZHAO Fujin, GUO Wei
2025,52(1):139-145, DOI: 10.12143/j.ztgc.2025.01.019
Abstract:
The development and utilization of geothermal energy is of great significance for achieving energy conservation， emission reduction， and green and low-carbon development. In response to the problems of no application precedent and incomplete technical system of non-interfering heating technology in Shanxi shallow high-temperature geothermal fields， a pilot test technology for the development and utilization of non-interfering heating in Shanxi shallow high-temperature geothermal fields is proposed by studying the geological characteristics of the experimental area， integrating key technologies such as drilling technology， underground heat exchange， and heating control. The experiment shows that the drilling test hole has a depth of 295.72m， and the temperature at the bottom of the well has been measured to be 109.9℃. Using non-interference underground heat exchange and heating technology， the system has a circulating flow rate of 16.90m3/h， which can meet the heating needs of a temporary building with an area of 2500m2 with an average indoor temperature of 22℃. The non-interference heating pilot test was successful in the shallow high-temperature geothermal field in Shanxi， and the on-site heating effect was good. The test results provide valuable experience and technical support for the development and utilization of shallow high-temperature geothermal fields in Shanxi.
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2025,52(1):146-152, DOI: 10.12143/j.ztgc.2025.01.020
Abstract:
The stability of the slope of an open-pit mine is mainly affected by geological structures such as faults and joint of rock mass. In order to identify the distribution characteristics of the rock mass structural， the Reflex ACT Ⅲ tools were used to unify thecore orientation of 4 geotechnical survey holes. However， the proportion of highly reliable core orientation data for each borehole only 8.05%~34.29%， due to therock mass fragmentation and joint development near the contact zone between granite intrusions and sedimentary rocks， which affects the accuracy of core orientation. Therefore， this article took OTV/ATV survey to obtain lithology and structural characteristics， relationships and direction data effectively and improve the accuracy of geological structure information data of core orientation， through high-resolution， continuous and oriented 360° borehole wall images. Based on this， failure mode of the open pit mine was studied by equatorial polar projection theory and dynamic analysis. According to the result， the main failure mode is wedge sliding failure， with a probability of 12.66%~34.99%， followed by plane sliding， with a probability of 3.40%~20.36%， which provides the foundation for open-pit mining slope control.
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LIU Wu, FAN Jingui, HAO Long, LIU Yanpeng, XU Linshan, JIN Shanshan
2025,52(1):153-161, DOI: 10.12143/j.ztgc.2025.01.021
Abstract:
The dangerous rockmass studied in this paper is located at the foundation site under a small ancient pavilion，under the premise of protecting ancient buildings，the difficulty of controlling dangerous rockmass increases obviously. Because of the high and steep location of the dangerous rockmass， and a inverted pyramidal collapse cave chamber has been formed below it，moreover， there is a landscape path of the characteristic landscape park of Shijingshan ancient construction mountain body located at the foot of the steep slope of the dangerous rockmass， severe challenges to the treatment of dangerous rockmass are posed. After comparing and selecting several schemes， the measure of I-steel inclined bracing inner support ring under the dangerous rockmass is taken. As the observation during the construction and upon completion， it has a good effect on the protection and treatment of small ancient pavilion foundation. This study can be used as a reference for dangerous rock treatment projects under similar special conditions.
