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    Volume 51,2024 Issue 6
      综述
    • LI Yazhou, SUN Youhong, ZHANG Nan, FAN Xiaopeng, LI Bing, GONG Da

      2024,51(6):1-13, DOI: 10.12143/j.ztgc.2024.06.001

      Abstract:

      It is of great significance to carry out intermediate-depth and deep ice-core drilling projects in polar regions for obtaining paleoclimate information and predicting future ice sheet evolution. Since the 1960s, countries around the world have completed 26 intermediate-depth ice-core drilling projects and 14 deep ice-core drilling projects in polar regions. At present, there are still five deep ice core drilling projects in progress, which are Dome A, Beyond EPICA, MYIC, Dome Fuji and Hercules Dome. Russia is also planning a deep ice core drilling project at Dome B. At present, China has only implemented one intermediate-depth ice-core drilling project, and the depth of the deep ice-core drilling project has just broken through 800m. Compared with Europe, the United States, Japan, Russia, China has less drilling experience, low degree of equipment independence, and relatively backward technical level in the field of intermediate-depth and deep ice-core drilling technology. Therefore, China should actively develop deep ice-core electromechanical drill with independent intellectual property rights, accelerate the implementation of Dome A deep ice-core drilling project, carry out intermediate-depth ice-core drilling and ancient blue ice drilling projects, break through key technologies such as rapid ice drilling and directional ice-core drilling technology, so as to promote the development of China’s polar ice-core drilling technology and improve its influence in the field of polar ice core science.

    • 钻探理论与方法
    • TANG Fenglin, ZHAO Rongxin, NESKOROMNYH V.V., LI Bo, ZHOU Xin, DUAN Longchen, CHIKHOTKIN V.F.

      2024,51(6):14-23, DOI: 10.12143/j.ztgc.2024.06.002

      Abstract:

      Percussion rotary drilling is an important method of drilling and widely used in geological exploration. Traditionally in percussion rotary drilling application of impact pulse is centric,but not eccentric. Russian experts have put award fragmentation of rock by application of eccentric impact pulse in order to improve the result of the fragmentation. That is a new concept and an innovation. The experimental research has been proved, that in percussion rotary drilling by eccentric impact pules in rock not only vertical normal stress are created, but also tangential shear stress created and it is beneficial to improve the result of rock fragmentation and rising of drilling rate. In drilling dolerite and marble at eccentricity E=1~2mm the mechanical drilling rate and bit penetration per revolution are increased substantially in comparison with E=0mm. Matching with the mentioned above the drill bit for eccentric percussion rotary drilling has been developed and the bit patent obtained, strengthening the result and role of the eccentric percussion rotary drilling further in geological exploration. It is suggested that further research on eccentric percussive rotary drilling should be carried out in China.

    • FAN Cunhan, ZHU Chaofan, LIU Zhao, SHUI Haoche, DONG Guangshun, LI Yanwei, GUO Wei

      2024,51(6):24-31, DOI: 10.12143/j.ztgc.2024.06.003

      Abstract:

      Underground in-situ conversion is an inevitable trend of industrialized development of oil shale, and the autothermic pyrolysis in-situ conversion process (ATS) is a compound and efficient heating method to realize underground in-situ conversion of oil shale. In order to investigate the influence of different high-temperature carrier gases in the preheating stage on the effect of autogenous thermal in-situ conversion of oil shale, this paper took the oil shale in Fuyu area of Jilin, China, as an example, and injected four high-temperature gases, namely, nitrogen, air, steam, and carbon dioxide, into the preheating stage to conduct numerical simulation analysis, and compared the differences in the final oil and gas yields and the energy recovery rates. Taking the high-temperature nitrogen injection group as the control group in the preheating stage, the results showed that the time needed to complete the extraction by injecting high-temperature air, steam and carbon dioxide was reduced by 22%, 39% and 12%, respectively, and the maximum energy recovery rate was increased by 55%, 86% and 23%, respectively, and the total oil production was reduced by 5%, increased by 18% and reduced by 11%. From the perspectives of mining completion time, energy recovery rate and total oil production, steam injection preheating had the best effect. Therefore, a comprehensive comparison showed that the autogenous thermal extraction method of steam injection preheating could effectively increase the oil production, reduce the time required for extraction, and improve the energy utilization rate.

    • HAN Zelong, LI Xiaoyang, ZHAO Ming, SONG Gang, ZHANG Xin, JIANG Yafeng, TIAN Yingying

      2024,51(6):32-38, DOI: 10.12143/j.ztgc.2024.06.004

      Abstract:

      The pressure holding coring technology can keep the extracted core under in-situ condition, minimize the loss of important data in the core, and then accurately obtain important formation parameters which can calculate the reserves of mineral resources. In this paper, the ball valve mechanism of pressure core sampler is studied by numerical simulation, and its dynamic characteristics are explored to optimize the ball valve mechanism, and increase its sealing reliability. The results show that with the increasing of thrust force on the ball valve, the shorter the closing time of ball valve, but the vibration generated increases, which is easy to cause seal failure. Thus, the small thrust force is selected to help improve the sealing reliability. With the decreasing of friction coefficient, However, the vibration generated increases, making the leakage risk of ball valve much bigger. When the ball valve is closed, the pressure simulation of 30MPa is conducted. The maximum contact stress and the maximum strain are both within the allowable range of ball valve.This study are meaningful to guide the optimal design of ball valve mechanism and improve its working reliability.

    • YANG Kuancai, MENG Yanjie, XU Quanwei, YANG Xianyu, CAI Jihua

      2024,51(6):39-47, DOI: 10.12143/j.ztgc.2024.06.005

      Abstract:

      There are many challenges in the process of geological drilling, among which the problem of leakage is particularly prominent, especially in fractured formations, which occurs more frequently. Therefore, it is of great practical significance to develop a drilling fluid system suitable for loose broken formation to maintain rapid drilling in broken formation. The inert material and formula suitable for plugging in the broken formation were determined by optimization experiments. Meanwhile, Super Absorbent Polymer (SAP) was prepared by aqueous solution polymerization, and the water absorption ratio was more than 100 times under the condition of 0~100℃. The non-permeable drilling fluid loss instrument was used to optimize the particle size and concentration of SAP, and 0.3% of 4~8 mesh SAP was the best choice. Finally,the formula of the drilling fluid system for plugging the broken formation was optimized: water+8%bentonite+0.1%xanthan gum+0.6%HV-CMC+2%walnut shell+1%mica sheet+2%specialty fiber+0.3%SAP of 4~8 mesh. The drilling fluid system can completely plug the sand filling bed of 10~20 mesh, the loss is 0 mL at 0.69MPa pressure, and has good rheological stability in the range of 0~60℃. The apparent viscosity is between 25~48mPa·s, the dynamic shear force is 6~18 Pa, the API filtration loss is 7~11mL, and the lubrication coefficient is 0.311. It shows a good application prospect in plugging loose broken strata.

    • LIU Dan, CHEN Jianyao, HOU Yue, HE Nan, LIU Jingtao, ZHOU Shaowu

      2024,51(6):48-58, DOI: 10.12143/j.ztgc.2024.06.006

      Abstract:

      With the continuous improvement and expansion of the application scope of active magnetic measurement technology represented by SmartMag Drilling Target-Hitting Guide System, it will be more applied in high-temperature underground environments such as geothermal well development and deep-sea mineral resource exploration in the future. High temperature often becomes a bottleneck problem that restricts the normal operation of instruments.In order to further improve the temperature resistance performance of the SmartMag system, this article adopts passive thermal management method and uses finite element method to simulate the phase change heat storage characteristics of the vacuum flask. It explores the optimal coupling length of the heat absorbing body and compares the phase change materials with the best temperature control ability horizontally. It analyzes the changes in axial temperature and phase state of the heat absorbing body inside the vacuum flask over time.The results show that the optimal coupling lengths are 400mm for the upper absorber and 250mm for the lower absorber. After operating the insulation cylinder at 150℃ for 6 hours, the utilization rate of phase change latent heat of the upper absorber is 96.7%, and the utilization rate of phase change latent heat of the lower absorber is 70.5%. The minimum temperature of the circuit board is 63.48℃, and the temperature control effect of low melting paraffin is the best.

    • ZHOU Zhongming, CHEN Junhai, LI Dandan, SUN Qianqian, JIA Yanjun, JIANG Jiajun

      2024,51(6):59-66, DOI: 10.12143/j.ztgc.2024.06.007

      Abstract:

      Dengying Formation stratum has become an important stratum for Sinopec to increase natural gas storage and production in Sichuan Basin and improve national energy security. Due to unclear understanding of the mechanical properties of dolomite in the ultra-deep high-temperature Dengying Formation, it often leads to instability of the dolomite wellbore. By conducting uniaxial compressive strength experiments of dolomite at 25℃ (room temperature), 100℃, 150℃, 180℃, 200℃, and 220℃, the uniaxial mechanical strength and deformation characteristics of dolomite were revealed. The dolomite in the Dengying Formation will exhibit significant brittleness enhancement with increasing temperature within a certain temperature range (100~220℃), which is believed to be the reason why the peak strength of the dolomite in the Dengying Formation decreases with increasing temperature. Based on the strain Equivalence principle, the damage deformation constitutive model of dolomite in Dengying Formation after high temperature is established. The comparative study shows that:(1)The stress-strain curve drawn by the constitutive model is in good agreement with the experimental curve, and the model can fully reflect the damage process of dolomite in Dengying Formation at different temperatures; (2)This model can accurately characterize the strength and deformation parameters of dolomite at different temperatures, providing a more scientific and rigorous model for wellbore stability analysis, and improving the geological understanding of ultra-deep to ultra-deep complex formations in key areas and the ability to prevent and control complex faults during drilling and completion.

    • CHEN Zhiming, ZHAO Hu, WEN Dayang, FENG Qinghao, LIU Tianle

      2024,51(6):67-76, DOI: 10.12143/j.ztgc.2024.06.008

      Abstract:

      The prediction of the hook load during casing insertion is one of the key factors for success. Due to its special wellbore trajectory, the frictional resistance during casing insertion in horizontal wells is higher than that in conventional wells. Therefore, accurately predicting the frictional resistance of casing insertion plays an important guiding role in the design and construction of horizontal well cementing. At present, many friction prediction analysis models have been developed in the industry, and relevant theoretical research and case analysis have been carried out. The commonly used analysis methods include Soft-String Model, Stiff-String Model and finite element method. Subsequent scholars used various theoretical methods to consider the friction analysis model of casing under various stress conditions on the basis of the three methods, but there is currently no relevant research that summarizes and analyzes the advantages and disadvantages of existing model algorithms, making it impossible to conduct model optimization in specific applications. Therefore, according to different basic theories, this paper classifieds and analyzes the current casing friction models, and discusses the existing technical bottlenecks in casing friction research and prediction as well as the next development direction, in order to provide guidance and help for the in-depth integration development of casing friction analysis in the future.

    • 钻探技术与装备
    • QIN Rulei, GAO Jieyun, YU Yanjiang, CHEN Haowen, LI Qiang, HE Guolei, SU Xianghui, XU Benchong

      2024,51(6):77-84, DOI: 10.12143/j.ztgc.2024.06.009

      Abstract:

      As the core functional unit of riserless mud recovery system, the mud lifting centrifugal pump drives the mud stored in the suction module to carry rock cuttings recirculate back to the drilling platform through the return pipeline. Previous designs of the riserless mud recovery system primarily employed disc pumps as the lifting unit, with specific structural design and theoretical analysis conducted around them.However, there has been limited research on multi-stage centrifugal pumps, which offer superior hydraulic performance. In this study, we focus on the theoretical basis and specific parameters of a multi-stage centrifugal pump,and develop a computational model using CFD-DEM coupling calculation to conduct a full-scale flow field simulation.This simulation investigates the impeller design, flow field characteristics, internal particle distribution patterns, and mud rock transport patterns within the pump.The results validate the centrifugal pump’s good particle permeability under design conditions.Furthermore, we conducted hydraulic performance tests on a centrifugal pump prototype using a mud lifting test bench. The test resultsindicate that the pump exhibits satisfactory operational working characteristics and hydraulic performance, meeting the design requirements for application in deep-sea riserless drilling operations.

    • HU Li, LI Junping, TANG Zhijian

      2024,51(6):85-90, DOI: 10.12143/j.ztgc.2024.06.010

      Abstract:

      Aiming at the low efficiency of horizontal directional drilling in hard formation, the self-sharpness of the bit was improved by the hard brittleness of FeCoCu pre-alloy matrix and the hard silicon carbide particle to weaken the matrix. The layered structure design is used to alternate the high and low wear resistance layers along the radial direction of the bit. The thickness of low wear resistance and high wear resistance were designed to be 1.0~1.5mm and 2.5~3.5mm respectively, to realize simultaneous wear of high wear resistance layers and low wear resistance layers and improve drilling efficiency. The bits have been successfully applied to horizontal directional drilling in hard potassium feldspar granite formation, using the combination of FeCoCu pre-alloy matrix and stratified matrix structure, with the average ROP of 0.8~1.5m/h and the drilling life of 30~40m. Compared with the ordinary concentric sharp tooth bit, the ROP has been increased by about double, and the drilling life has been increased by more than 30%.

    • XIE Xiaorong, CHEN Xiaobin, DONG Xiaobin, TANG Lubo, LIN Fantong, LUO Jiarui, SU Dingli

      2024,51(6):91-98, DOI: 10.12143/j.ztgc.2024.06.011

      Abstract:

      The advancement in the drilling technology of large displacement wells has provided a great potential for significantly improving the efficiency of extracting unconventional energy sources such as shale gas. However, the high friction between the drilling rods and the wellbore during the process of large displacement well drilling reduces the drilling efficiency. One effective solution to address the technical challenges of high friction and severe drag in the current construction process of extended reach wells or horizontal wells is to incorporate drag reduction tools capable of generating oscillations into the downhole drilling tool assembly. However, currently, there are few types of such tools, and they generally suffer from complex working mechanisms, difficulties in structural design, and excessively high tool pressures. Therefore, this paper proposes a reverse feedback oscillating jet pressure pulse drag reduction tool with low pressure and no moving parts. Visual experiments and numerical simulations were conducted on this tool, and the working mechanism of the jet oscillator was elucidated by monitoring the evolution of the internal flow field of the tool. The results showed that the generation of pressure pulses is composed of phenomena such as the wall attachment and detachment of the jet, as well as the growth and dissipation of internal vortices in the tool. Furthermore, the pulsation performance of the tool was studied, revealing its operational performance under different conditions such as flow rate, drilling fluid density, viscosity, etc. Structural optimization was carried out for conditions of low drilling flow rates, expanding the operational range of the tool. This paper can provide new insights for the design of large displacement well drilling tools.

    • MA Tan

      2024,51(6):99-105, DOI: 10.12143/j.ztgc.2024.06.012

      Abstract:

      During the drilling process, accidents of screw drilling tools breaking and falling often occur. For lightweight falling objects caused by accidents such as detachment of the outer shell of the screw drilling tool and core pulling due to rotor fracture, the applicability and success rate of using conventional slip salvage barrels are insufficient. Based on this, a screw drilling tool three slip eccentric fishing barrel was designed, which drives the upper, middle, and lower slips to contract and clamp the conjugate annular space through the conical guide surface of the fishing barrel, achieving effective fishing of this type of falling objects. The eccentric arrangement structure design of the three slips increases the effective clamping area and improves the comprehensive fishing force of the fishing barrel on the screw drilling tool. Based on the working principle of the fishing barrel, a calculation formula for the conventional clamping force of the slip and the squeezing clamping force was established. By comparing, it was found that the conventional clamping stress of the slip required for the three eccentric fishing barrel can be reduced by 50.46%, and the bite depth of the fishing tool can be reduced by 13.92%. The trial produced fishing tube has been put into salvage practice on the construction site, indicating that its structural design is reasonable and its salvage performance is reliable.

    • SHAO Shuai, SU Bo, WANG Rongjing, ZHANG Tao, LU Chunhua

      2024,51(6):106-110, DOI: 10.12143/j.ztgc.2024.06.013

      Abstract:

      The development of automatic monitoring system for core filling rate is to fill the shortage of core condition monitoring in the coring process. The automatic monitoring system is composed of main controller, reserved temperature and pressure monitoring module, Hall sensor module, data storage module and serial debugging module. Among whcih, the principle of core status monitoring is based on Hall effect. The coring speed range of the system can be monitored in 0~30 mm/s, and the monitoring accuracy is about 1%. The system uses STM32 single-chip microcomputer, large-capacity memory, high-speed USB interface and so on, which has the functions of online debugging, programming and upgrading. The sea tests were made, and the results show that the system can automatically monitor the process of core penetration into the core tube at a water depth of 3000m (a hole bottom pressure of 0~35MPa), which can provide theoretical guidance for the selection of field sampler type and the optimization of working parameters of the sampler, and has a broad application prospect.

    • 工程实践与应用
    • ZHAO Hongbo, ZHANG Long, SHEN Lina, ZHANG Jiaodong, LIU Xufeng, WANG Dandan, MENG Xianglong, HU Hao, ZHU Disi

      2024,51(6):111-118, DOI: 10.12143/j.ztgc.2024.06.014

      Abstract:

      The Paleogene sedimentary thickness in the Sanmenxia Basin in Southern North China is large and continuously distributed, with developed dark mudstone. Through the deployment of drilling projects, new discoveries of oil and gas in small and medium-sized basins can be assisted. However, the geological environment for drilling in this type of reservoir is complex, with frequent sand and mudstone interlayers, which can easily cause engineering difficulties such as bit mud entrapment, wellbore collapse, block falling, coexisting risks of leakage, and difficulty in drilling. Through the optimization of drilling tool combination and wellbore structure, research on drilling fluid technology in different sections, development of PDC irregular tooth drill bits, and research on the drilling process of “low speed + medium drilling pressure + screw + high-efficiency PDC drill bits”, effectively solved the problems of wellbore stability and drill bit selection. In the actual drilling of Well YXD1, the average mechanical drilling speed of comprehensive drilling reached 5.67m/h, that improved 30%, which shortened the drilling cycle by 10 days compared to the design. Innovations have formed a “new, superior, and fast” drilling and completion technology system for sand and mudstone interlayers in the Sanmenxia Basin, including a mud pack drilling fluid technology system, a long open hole wellbore protection drilling fluid technology system, an efficient PDC shaped cutter drill bit acceleration technology for sand and mudstone interlayers, and a “two low and one high” variable density cement slurry cementing technology that can be promoted. This can provide useful reference for drilling engineering design and construction in similar regions.

    • CHEN Haodong, WU Yanhui, MA Chuanhua, HUANG Honglin, LUO Ming, LI Wentuo, DAI Rui, LIAO Gaolong

      2024,51(6):119-124, DOI: 10.12143/j.ztgc.2024.06.015

      Abstract:

      In the ultra-deep and ultra-shallow reservoirs (“double ultra” for short), problems exist such as difficult coring operation, low success rate, high operation cost, and lack of reference experience. In view of this, the analysis of the coring difficulties without risers is carried out, the corresponding technical countermeasures are put forward, and a set of efficient coring scheme is formed. The results show that in the “double ultra” environment, the reservoir is dominated by unconsolidated and loose argillous sandstone, and the coring operation faces the problems and challenges of “blocked core”, the difficulty of controlling displacement and bit weight, and the high cost of ultra-deep water operation. The Rb-8100 fully enclosed conserved coring tool and HSC043-8100 coring bit are selected, corporated with small perameter mode of small displacement (200L/min), low speed (15~40r/min) and stepped bit weight (2~10t). The self-made net diverts seawater at the bit and protects the bottom core. The pilot test of riserless coring was carried out in “double ultra” gas field in South China Sea, and the core recovery reached 100%. It is the first time to realize the efficient coring operation in “double ultra” reservoirs, and lays an important foundation for the later development of ultra-deep and ultra-shallow reservoirs gas field.

    • WANG Yongjun, NIE Dejiu, YUAN Baohong, YUAN Baoxin, ZHAO Changliang, ZHANG Tao, LIU Zhenxin

      2024,51(6):125-131, DOI: 10.12143/j.ztgc.2024.06.016

      Abstract:

      In the drilling construction of high-temperature geotherm in the Tianyang Basin, affected by the lithology and high temperature of the hard rock strata of the metamorphic rock system, the cone bit has low mechanical drilling efficiency, serious wear, and short service life, which seriously affects the drilling construction. As a result, the application of PDC bit was explored. Aimed at the lithological characteristics, the key technologies such as the selection and layout of bit body, blade, profile and composite pieces were explored and optimized in drilling practice. A PDC bit with good impact resistance and suitable for metamorphic hard rock formations is developed, which effectively improves the mechanical drilling speed and reduces the drilling cost, which provides technical support for the smooth implementation of the high-temperature geothermal drilling project in the Tianyang Basin.

    • LUO Han

      2024,51(6):132-140, DOI: 10.12143/j.ztgc.2024.06.017

      Abstract:

      The tight sand formation reservoir of the Xujiahe-2 Formation in Xinchang Structure, western Sichuan has failed to form large-scale commercial development for a long time due to the unbalance of cost of drilling and benefit of production. In view of this phenomenon, through the series of scientific studies on the key drilling processes based on the optimization of setting positions, the hole size, the hole trajectory optimization, the combined drilling of the drilling tool, the low cost of the rotating guide tool in this paper. The comprehensive application of this technology in the block has achieved the breakthrough of shortening the shortest drilling cycle from 231.1 days to 95.7 days, achieved good application results, and realized the benefit development of the block.

    • SHUAI Hongyan, LI Guangcheng, HUANG Junjie, DENG Min, WANG Jianxiao

      2024,51(6):141-151, DOI: 10.12143/j.ztgc.2024.06.018

      Abstract:

      Taking a foundation pit project in Wuhan as the background, based on two observation indicators of water level drop inside and outside the confined layer pit and surface settlement outside the pit, a three-dimensional numerical calculation model for group well precipitation was established using finite element software ABAQUS for numerical simulation analysis. By setting multiple calculation conditions, under the conditions of different insertion ratios of suspended waterproof curtains λ, the influence of different well screen lengths L and filter tube burial depth H on the water level drop inside and outside the confined layer pit and surface settlement outside the pit was studied. The research results indicate that the impact of the insertion ratio λ on the water leverl drops inside and outside the confined layer pit and the surface settlement outside the pit is much greater than that of the length L and burial depth H of the well screen in the dewatering well. When the λ is between 0.4 and 0.6, there is a large space to increase the water level drop inside the confined layer pit or decrease the water level drop outside the confined layer pit by changing the length L and the burial depth H. When λ exceeds 0.6, it has a good water blocking effect. The buried depth H of the well screen should be located at the top of the confined aquifer, and the length of the well screen L should not exceed 0.4 times the thickness of the confined aquifer M.

    • MA Ning, DENG Yue, LING Xue, YANG Linrui, QIAN Yang, LIU Yi, HUANG Shijie

      2024,51(6):152-159, DOI: 10.12143/j.ztgc.2024.06.019

      Abstract:

      This paper focuses on the pressure shock wave generated by the electric explosion of the wire acts on the hole wall of the soil layer and form the belled piles caused by squeezing the soil at the bottom of the pile. The relationship function and simulation model between the explosive energy of the wire and the shock wave pressure are established, and the relationship between the discharge parameters and the shock wave intensity is analyzed. The relationship between shock wave pressure and soil deformation is established, and the pressure required for the deformation of clay soil is calculated. The models of belled pile and equal diameter pile were made to verify the deformation characteristics of soil under the electric explosion of the wire, and the bearing capacity and pullout resistance of the two piles were compared and analyzed. Based on the electrical and technological parameters of the high-voltage pulse bottom expanding technology model test, the first high-voltage pulse belled pile with a diameter of 0.8m was constructed in China, and the “irrigation-expansion” integrated construction method was developed.

    • 地学科普
    • YAN Jia, WANG Wen, ZHANG Hengchun, CAO Longlong, XUE Qianbing, LIANG Nan, SHI Shanshan, WANG Zhigang, WANG Kaili

      2024,51(6):160-167, DOI: 10.12143/j.ztgc.2024.06.020

      Abstract:

      Drilling is the most direct engineering technology means for the exploration and development of energy and mineral resources. As a powerful tool for breaking rock and soil, downhole power drilling tool have the advantages of reducing consumption and increasing drilling speed, as well as reducing the risk of downhole accidents, it either directly drives the bit to form sliding drilling, or combines the top drive (or rotary) to form composite drilling. In order to prompt more technical personnels to understand the downhole power drilling tool, and develop new functions and new instruments based on its drilling advantages and technical characteristics, this paper introduces the use, main type, working principle and development history of the downhole power drilling tool from the perspective of popular science, and compares the advantages and disadvantages of different downhole power drilling tool. Finally, combined with the new requirements posed by the new drilling situation of deep wells, ultra-deep wells on the drilling tool, techniques and so on, as well as the application trend of other new technologies in drilling engineering such as materials, measurement and control, intelligence, etc., it pointed out the upgrading and technological innovation development direction for the current mainstream downhole power motor.

    • Editorial Office of 《Drilling Engineering》

      2024,51(6):168-174, DOI: 10.12143/j.ztgc.2024.06.021

      Abstract:

      Total content of 《Drilling Engineering》 2024

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    • Influence of Wear on Rock contact area of V-shaped Cutter PDC Bit

      QI Renze, REN Lei, BU Changgen

      Abstract:

      With the increasing demand of deep-sea and deep-earth drilling, the wear of downhole drilling tools using traditional PDC bit is serious, which cannot fully meet the drilling requirements of deep wells in hard formation, so the special-shaped cutter PDC bit, especially the V-shaped cutter PDC bit, become the focus of research. At present, there are few studies on the influence of wear on rock contact area of V-shaped cutter PDC bit, so it is very important to study the influence of V-shaped cutter wear on its ROP. In order to calculate the contact area between the V-shaped cutter and the rock in the wear stage, by using the method of plane inclined intercepting the cylindrical surface where the composite piece is located, we deduce the expression of the contact area as a function of the wear height and the geometric parameters of the V-shaped cutter, such as chord length and tangent angle, and we analyze the influence of the geometric parameters of the V-shaped cutter and the wear height on the contact area and the contact pressure. The results show that: in the early stage of wear, the contact area of cylindrical cutter and V-shaped cutter is the same, when the composite piece wears to a certain stage, the contact area of V-shaped cutter is smaller, and the smaller the chord length and tangent angle are, the smaller the contact area is; under the same load, when the wear reaches to a certain stage, the contact pressure of the V-shaped cutter is larger compared to that of the cylindrical cutter, and it have the ability to cut deeper into the rock. When drilling rock formations, V-shaped teeth PDC drills can be used, by measuring the height of the cutting teeth wear and accurately calculating the contact area between the cutting teeth of the drill bit and the rock, it is convenient to adjust the drilling pressure in time to maintain a higher drilling speed; or optimize the geometric parameters of the V-shape teeth when designing, which is also conducive to improving the drilling efficiency.

      • 1
    • RESEARCH PROGRESS AND PROSPECTS OF LONG-TERM OBSERVATION DEVICES FOR OCEAN SCIENCE DRILLING AND EXPLORATION WELLS

      LYU Yang, XIONG Liang, TIAN Lieyu

      Abstract:

      Ocean scientific drilling is an important means of scientific exploration and research of the ocean floor, and has extremely important significance in many fields such as earth science, life science, and resource exploration. CORK (downhole long-term observation device) is an important supplement to ocean scientific drilling. Ocean scientific drilling mainly obtains core samples, while CORK focuses on long-term in-situ observation of drilled holes, which can fully utilize the drilling resources after drilling and achieve the transformation from short-term sampling to long-term dynamic observation of the seabed environment. Over the past few decades, the technological means of developing underwater observation equipment have also been continuously improved in this process. CORK has derived four new versions based on the initial development of CORK, which have evolved from single layer sampling to multiple layer sampling and can also perform in-situ testing. The new round of ocean drilling program led by our country is about to be implemented, and it is urgent to increase the research and development efforts of CORK technology, use our own resources and talents to build an underwater CORK observation system, and lay a solid foundation for quickly entering the ranks of world maritime powers.

      • 1
    • Research Progress of Oil Shale Reservoir Reconstruction Technology

      WANG Wenxuan, ZHAI Lianghao, XUN Yang, Li Hao, Peng Zhaocui, Xiao Huguo

      Abstract:

      Oil shale reservoir is a kind of sedimentary rock rich in organic matter. The proven reserves of oil shale resources in China rank third in the world. Realizing the commercial development of oil shale resources is one of the important measures to ensure the energy security of our country. Oil shale in-situ conversion process has the advantages of green environmental protection, small footprint and can develop deep oil shale resources. it is an important technical means to realize the efficient development of middle and deep oil shale resources. This paper introduces the application and research results of hydraulic fracturing technology, supercritical carbon dioxide fracturing technology, acidizing fracturing technology and clear water fracturing technology in the process of in-situ exploitation of oil shale, and compares the advantages and disadvantages of four kinds of reservoir reconstruction technology. Meanwhile, the current applications and progress of hydraulic fracturing technology in experimental research, numerical simulation and pilot test project were highlighted. Finally, the deficiency and future development direction of oil shale reservoir reconstruction technology are discussed.

      • 1
    • Research and Application of Multiple Leakage Layers Plugging Without Tripping Out Based on Fast Circulating Valve

      wuxia

      Abstract:

      Complex geological factors such as fractures, faults, weak surface structures in unconformity contact, and multiple pressure systems in Sichuan Chongqing region result in multi-layers and multi-mechanisms leakage in same open hole. In order to solve the problems of long plugging time caused by slow establishment of pumping channels for large-diameter plugging materials under traditional mode of replacing drilling tool assemblies for plugging operations and limited on-site application caused by poor stability of existing plugging tools. A repeatable on-off fast circulating valve that allows large-diameter plugging materials to pass through has been developed based on the working principle of quickly establishing a plugging channel by switching flow channels through ground injection of work balls. Through specific optimization designs of tool size, sliding sleeve structure, ball seat structure, basket and working ball group structure, the stability of tool structure is enhanced while matching the wellbore size and performance requirements of high-risk leakage section. It is allowed to use maximum material particle size of 10mm and maximum plugging slurry concentration of 40%. Based on the characteristics of different leakage type in long open hole section, a technical method for rapid plugging with fast circulating valves has been proposed, which involves multiple plugging methods for multi-leakage points encountered in longitudinal drilling and segmented plugging method for multi-leakage points simultaneously. The method can achieve plugging up to 5 leakage layers without tripping out and on-site test improved the efficiency of plugging operations by 74% and reduced the cost of plugging.

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    • Construction of Shallow Pore Pressure Profile and Exploration of Drilling Technology in Karst Landform Areas

      MENG Xianglong, Li Dayong, WANG Shengjian, Chi Huanpeng, ZHU Disi, YUE Weimin, ZHANG Jiazheng

      Abstract:

      During the drilling process of shallow strata in karst landform areas, a large number of complex situations such as leakage and water inflow occur. The widely developed fracture and cave network in the strata forms fluid migration channels, and the pressure difference between drilling fluid and formation water is also an important influencing factor. Conventional pore pressure prediction methods cannot effectively characterize shallow pore pressure. To explore the actual distribution of shallow pore pressure in karst landform areas, a shallow pore pressure profile based on the actual distribution of groundwater was constructed based on hydrogeological and fluid mechanics principles. The effectiveness of the profile was verified using the Qianxi exploration well drilling example. The results showed that there were multiple pressure zones in the shallow layer of karst landform areas, which were closely related to the distribution of groundwater: there was no pore pressure above the groundwater level; The calculation of pore pressure in the groundwater layer should be based on the groundwater surface, which is a typical low-pressure zone; The pore pressure of a confined aquifer depends on the difference in location between the recharge and discharge zones, and may manifest as high pressure, low pressure, or normal pressure. Analyzed the adaptability of plugging materials, clean water drilling, and air down the hole hammer drilling in karst landform areas. It is recommended to fully utilize hydrogeological data in drilling design to construct shallow pressure profiles, select drilling processes or drilling process combinations based on this, and determine the depth of drilling for each opening to avoid complex drilling situations and improve drilling efficiency. This study can provide reference for the design and implementation of drilling projects in karst landform areas.

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    • The Application of Dual-polymer Anti-collapse Drilling Fluid for Drilling in The Covering Layer

      yufuan, liuweiping

      Abstract:

      During the drilling process in the covering layer of Zhumadian area in Henan Province, drilling encountered the Quaternary clay layer, the sandy mudstone, the loose sandstone and mudstone interbedded with uneven thickness, difficult drilling wall protection, and prone to accidents such as block jamming, hole collapse and burial, taking core difficultly. Based on the geological and stratigraphic conditions and the drilling construction data within the area, the dual-polymer anti-collapse drilling fluid was used. Through the on-site application of the dual-polymer anti-collapse drilling fluid, the stability of the hole wall was good during the drilling process in the long open hole well section, without any incidents of falling or collapsing. The core monitor rate met the geological design requirements with reducing the depth of casing insertion and saving construction costs.

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    • Dynamic Characteristics Analysis of CDH-125 Valve-less Pneumatic Down-the-Hole Hammer Impact System

      Guo Naiming, Wang Qingyan, Luo Chaochun, Zhong Weiling, Li Haoxuan

      Abstract:

      This paper studies the impact dynamics process of the CDH-125 pneumatic down-the-hole (DTH) hammer, accurately analyzing the force state during the motion of the valveless distribution piston. Subsequently, based on the finite difference method, the thermodynamic and dynamic differential equations of the DTH hammer during its working process are iteratively solved to obtain the dynamic working characteristics of the DTH hammer piston and air chambers. These characteristics include the relative relationship between piston displacement and velocity, and the pressure and temperature exchange relationships in the front and rear air chambers. The results obtained from the finite difference method were compared and validated using the multiphysics simulation software SimulationX, showing a maximum speed discrepancy of 3% for the piston stroke, 19% for the return stroke, and 5% for the working frequency. Based on these results, further calculations and analyses of the gas viscous friction force between the piston and the inner cylinder were conducted. The results indicate that, compared to the ideal situation with non-viscous fluid, the viscous friction force reduces the working frequency of the DTH hammer by 0.15% per working cycle and increases the maximum energy consumption of the piston stroke by 0.05-1.34J per cycle. The impact of viscous friction on the dynamic performance of the DTH hammer cannot be ignored.

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    • Failure analysis of PDC spherical cutter for drill bit

      Zhao Hongchen, Meng Dezhong, Xu Liang, Ye Hongyu, Yue Wen

      Abstract:

      As one of the key technologies in the exploration and development of geothermal resources, the efficiency and effect of DTH hammer drilling largely depend on the performance of the drill bit, especially the quality and life of PDC spherical cutters. In response to the current issues such as low drilling efficiency and short service life due to the breakage, detachment, and severe wear of cutter in air-assisted percussive drill bits. This paper conducts a macroscopic and microscopic analysis of the PDC spherical cutter, investigates the causes of failure and the failure mechanisms, and proposes targeted measures for improvement. The results show that the main failure modes of PDC spherical cutters are tooth fracture, wear and fall off. The main reason for the failure of the cutter is that the cutter is damaged by tangential impact compression and normal tensile stress at the same time, while the poor performance of the cutter material itself, and the combination strength of the diamond layer and the cemented carbide matrix are also important reasons for the failure. In order to improve the performance and service life of PDC spherical cutters, the stress burden of the cutters can be reduced by optimizing drilling parameters and adjusting external operating conditions. In addition, innovation and improvement of the material formulation, structural design and manufacturing process of PDC spherical cutters is also an effective way to improve its impact resistance and wear resistance. Through these comprehensive performance improvement methods, the reliability of PDC spherical cutters can be effectively improved, thus improving the operational efficiency of downhole drilling and the service life of the bit.

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    • Design and analysis of continuous circulation valve

      CUI Shuying, CHEN Xiaojun, CHEN Genlong, ZHAO Ming, TIAN Yingying, ZHANG Xin, HAN Zelong

      Abstract:

      The continuous circulation valve can maintain the continuous circulation of drilling fluid when drilling is stopped, which can effectively solve the sediment at the bottom of the hole and the fluctuation of pressure at the bottom of the hole, especially for the horizontal drilling of oil and gas in the sea. In this paper, a continuous circulation valve is designed, the structure and working principle of the continuous circulation valve are introduced, the force analysis and structural optimization design are conducted on the strength of the body under extreme working conditions, and the side opening of the bypass valve with a safety factor greater than 1.5 times was selected; A finite element stress analysis is conducted on the bypass valve, which comprehensively analyzed the stress distribution and sealing pressure. The influence of changes in the half cone angle of the sealing pair and the thickness of the valve on the stress and sealing effect of the bypass valve is obtained. The half cone angle of the sealing pair and the thickness of the valve are selected, and the bypass valve sealing test and body strength test are conducted, proving that the strength and sealing performance of the continuous circulation valve meet the actual usage requirements.

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    • Research on geothermal reservoir types and formation damage mechanism

      LU Wei, WANG Jinliang, GU Chao, wanguangnan, ZHANG Han

      Abstract:

      The research on the formation damage mechanism of conventional petroleum reservoirs is relatively well-established, but there has been a lack of attention towards the type classification and formation damage mechanism of geothermal reservoirs. Currently, only two types of geothermal reservoirs - sandstone and karst - are recognized in the exploration and development of geothermal resources. Because of the unclear concept and type of reservoir, the incorrect drilling method, drilling fluid selection and wrong resource assessment are caused. Furthermore,there is no formation damage mechanism and damage assessment criteria, so that the geothermal well completion process is missing, and leads to small water volume, low temperature, and even abandonment.On the basis of a large number of geothermal engineering, this paper focuses on the research of geothermal reservoir types and formation damage mechanism, aiming at the outstanding problems and referring to the conventional petroleum reservoirs research results. Researches show that: (1) Geothermal reservoirs can be categorized into four types: porous, fissure, karst, and compound type; this categorization allows for more accurate drilling methods, selection of drilling fluids,and resource assessment.(2) The main modes of thermal reservoir damage are porosity blockage or failure in the structure; among these factors,damage caused by intrusion from drilling fluid as well as staticand dynamic pressure from liquid column within wells are inevitable common problems.

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    • Construction Technology Discussion of Ultra-long Horizontal Directional Pre-grouting Boreholes

      WANG Yihong, YANG Zengzhi, SHAO Dongmei, WANG Zhaoyang, LI Longbiao, CHANG Xishun, CHEN Xiaojun

      Abstract:

      In the periphery of long and deeply buried tunnels of water conservancy projects, along the tunnel axis of a wide range of fracture zones and water-rich areas, the use of the ground more than 1,000 meters of horizontal directional drilling pre-grouting ahead of the management, to achieve a good effect of the surrounding rock reinforcement and gushing water blocking, is a successful attempt in the water conservancy industry. This paper introduces the successful experience of drilling ultra-long horizontal directional pre-grouting holes with screw drilling tools in a project, and discusses the difficulties of powder removal in ultra-long horizontal drilling holes, coping with the problem of “back pressure”, the interference of strong magnetic field with the drilling measurement system, the measures of green exploration, as well as the problems of insufficient adaptability of drilling rigs, low efficiency of hard-rock drilling, and the influence of grouting on drilling in operation, etc. and the measures to solve them. and measures to solve the problems. The project has 4 main holes and 6 branch holes, the longest hole is 1427m, and the drilling workload is 8737.89m. The implementation of the project proves that the current directional drilling technology has the ability to drill accurately over long distances, which can provide a guarantee for the pre-grouting and over-treatment of the complex strata of the ultra-long tunnels and the related drilling projects.

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    • Research on a Drill Rate Prediction Model Based on Feature Selection Integrated with Particle Swarm Optimization

      XU Zhihua, JIANG Jie, ZHOU Changchun, LI Qian, REN Jun

      Abstract:

      Traditional drilling speed prediction models have often been constrained by issues such as high data dimensionality and feature correlation, resulting in limited efficiency and accuracy of drilling speed prediction. To address these issues, a drilling speed prediction algorithm model based on Particle Swarm Optimization (PSO) with integrated feature selection has been proposed in this paper. Based on data preprocessing, three key parameters, threshold_1, threshold_2, and threshold_3, have been chosen as optimization targets, and a fitness function has been constructed by combining historical data and the Particle Swarm Optimization algorithm, thereby establishing the drilling speed prediction model. Subsequently, the proposed drilling speed prediction method has been validated using actual drilling data and compared with traditional machine learning algorithm models. Experimental results have shown that the proposed Particle Swarm Optimization-based integrated feature selection algorithm has achieved higher efficiency and accuracy in feature selection. The accuracy of the four machine learning drilling speed prediction models trained using the optimized integrated feature selection results has been improved by 59%, 1%, 3%, and 1%, respectively, compared to before optimization, and by 24%, 2%, 4%, and 3%, respectively, compared to models trained using all features. This paper has provided an effective feature selection method for cases where too many feature parameters have been extracted in drilling engineering, and it offers significant guidance for the practical application of feature selection algorithms in the engineering field.

      • 1
    • Development and performance characterization of PVA modified PLA fiber composite geothermal temporary sealing cement

      CUI Xiyue, TAN Huijing, CHEN Yao, ZHENG Yuntian, WANG Yuhao, YE You

      Abstract:

      Formations with developed fractures are more likely to receive better water supply, and severe leakage during drilling requires the use of cement for sealing, but this can easily cause reservoir damage problems. In this paper, a geothermal temporary plugging cement is developed based on degradable fibers, which has a low permeability during drilling, plays the role of wall protection and plugging, and partially degrades to provide a channel for the output of geothermal fluids after the completion of the well. Based on the preparation, modification and characterization of PVA-coated PLA fibers (PVA-PLA), the effects of the modified fibers on the performance of the cement paste and the performance of cemented cement stone before and after high-temperature hot-water immersion was investigated and the mechanism. The results showed that: the regulation of the degradation properties of polymer fibers can be achieved by coating, heat treatment and silane modification; the compressive strength of PVA-PLA fiber cementite at 60℃ was 19.8MPa at maximum, and the porosity was 28.88% at maximum after immersion at 90℃, which was most in line with the requirements of low-temperature plugging and high-temperature unplugging; the coating of PVA at 60℃ reduced the contact between PLA and cement matrix, and the PVA-PLA fiber cementite at 90℃ was more suitable to the requirements of low-temperature plugging and high-temperature unplugging. The PVA membrane dissolved and PLA exposed to cement alkaline environment was hydrolyzed and consumed during hot water immersion at 90℃, which resulted in the formation of more >200nm pores in the cement stone. The PVA-PLA fibers remain intact and plug with the cement stone at low temperature, and the fiber degradation at high temperature forms a channel inside the cement stone and unblocking, which can support the broken pore wall and at the same time, realize partial unblocking of geothermal wells under high temperature hydrothermal conditions.

      • 1
    • Finite element numerical simulation analysis of packer-type expansion pipe

      Liyunpeng, Yinfei, sunxiao, Fengjianyue, Liuyi, Chenzhiang, Zhengyunfei

      Abstract:

      The packer expansion tube technology has been developed for the hydrogeological exploration of wall protection and the repair of damaged well pipes. It has the characteristics of low cost and simple process. In order to make the packer meet the requirements of the expansion pipe, the expansion mechanism of the packer is improved. The packer is used to test the pipes with different properties. According to the test results, 316L stainless steel is selected as the expansion pipe. In order to study the relationship between the expansion pressure and the change of the length and thickness of the expansion tube during the two expansions of the packer-type expansion tube, the expansion process of the expansion tube with Φ219 mm and wall thickness of 4 mm was numerically simulated by Abaqus software to obtain the change of stress and strain during the expansion process, and field tests were conducted on the expansion tube with the same specifications. Then comparing the simulation results with the test results, it is concluded that the simulation results are basically the same as the actual demonstration results, indicating that the numerical simulation results can be used as a reference for the actual construction.

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Sponsor:China Geological Survey
Organizers:China Mining News & Institute of Exploration Techniques, CAGS
Edited Published:Editorial Office of Drilling Engineering
Master Edit:SUN Youhong
ISSN:2096-9686
CN:10-1730/TD
Postal code:2-333