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

QI Renze, REN Lei, BU Changgen

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

LYU Yang, XIONG Liang, TIAN Lieyu

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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.
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Research Progress of Oil Shale Reservoir Reconstruction Technology

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

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

wuxia

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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

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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

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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

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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

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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

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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

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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

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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

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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.
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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

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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.
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Finite element numerical simulation analysis of packer-type expansion pipe

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

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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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Volume 51,2024 Issue 6

综述

钻探理论与方法

钻探技术与装备

工程实践与应用

地学科普

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