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Design and simulation analysis of continuous coring parameters in directional drilling

HAN Zelong, LI Xiaoyang, SHI Shanshan, WANG Yingli, ZHOU Qingquan, MA Yinlong, TIAN Yingying

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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, the 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, complex force on drilling tools and difficulty in continuous core acquisition, the effects of weight on bit and rotation speed on drilling efficiency, drilling speed and build-up rate on directional coring were studied by simulation. The simulation analysis results show that the weight on bit and rotation speed are proportional to the drilling speed, build-up rate and bend-joint stress. When the weight on bit is more than 30 kN and the rotation speed is more than 230 r/min, the build-up rate of 6°/30 m can be satisfied. The formation stress under the action of weight on bit is more concentrated and the extension depth is small, while the formation stress distribution under the action of rotation speed is wide, reflecting different rock breaking effects. Based on the comprehensive consideration of drilling tool life, the preferred weight on bit is 25~30 kN and the preferred rotation speed is 230-300 r/min. The contact stress between the core and core tube becomes larger with the increase of build-up rate, but the final contact stress will be kept within the stable range. The maximum contact stress was 514.7 MPa at build-up rate of 9°/30 m. This contact stress was less than the yield strength of coring tube. The above simulation provides theoretical support for the coordinated optimization about drilling parameters and deviation capacity of directional continuous core drilling tools.
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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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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

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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

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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

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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

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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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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

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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.
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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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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.
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Research on the Pick Arrangement Pattern of Rotary Drilling Buckets Based on Pick Cutting Test

maning, huyawei, xiezhiyong, xiaodangui

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Abstract:

During the construction of rotary drilling rig, the efficiency of rock drilling is closely related to the pick arrangement of core barrel. The key pick arrangement parameters of core barrels are studied by using pick cutting test system. Three-dimensional load, crushing volume, deformation displacement, broken morphology and other data were collected during the test process. From multiple dimensions such as crushing specific power, cutting resistance, load fluctuation, and pick spin, the controlled variable method is applied to conduct pick cutting experiments, quantitatively evaluating the effects of cutting angle, tooth deviation angle, cutting sequence, tooth tip height difference, and tooth tip trajectory spacing on rock cutting. Research has shown that there is an optimal combination of tooth arrangement parameters that match the geological properties. Taking drilling into granite formations as an example, the optimal range of tooth arrangement parameters was determined, which are: cutting angle 68-72 °, tooth deviation angle 5-15 °, skip cutting, tooth tip height difference of about 3 mm, and tooth tip trajectory spacing of about 30 mm. According to the test results, the drilling efficiency is increased by 13.64% and the cost of unit footage is reduced by 39.13%. The research results are of great significance for guiding the arrangement of the core barrels, reducing the gear loss and improving the drilling efficiency.
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Research progress on wellbore instability mechanics of deep stratified weak face reservoirs

Zhao Longfei, Yin Wubing

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Abstract:

Deep reservoir gas reserves are abundant. However, due to complex geological conditions, such as the development of holes and fissures, the existence of weak bedding surface and other factors, shaft wall instability has always hindered the safe and efficient exploitation of deep oil and gas reservoirs. A series of problems such as stuck drilling, well collapse and leakage caused by shaft wall instability will bring huge losses to the project. Therefore, it is very important to have a comprehensive understanding of the mechanism and research progress of borehole instability. In this paper, starting from the stability of borehole, the mechanical mechanism and development history are summarized. It is found that the development of weak bedding surface, multi-factor ground stress, rock physical and mechanical parameters, the existence of pore cracks and other factors are the main factors that lead to the weakening of mechanical strength and the instability of deep reservoir wall. For strata with weak bedding surface, the wellbore instability is more obvious, and the mechanical strength of rocks at different inclination angles is greatly different, and the rocks are more prone to hydration expansion along the bedding surface. Therefore, drilling engineering parameters and drilling fluid density should be reasonably optimized. This paper systematically summarizes the research of borehole stability mechanics and related aspects, in order to better understand the mechanical mechanism of deep reservoir borehole stability, and provide reference for practical production and engineering practice.
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Design of deepwater pressure simulation testing system based on KingView and PLC

LIU Xiaolin, GAO Jieyun, WANG Jiarui, CHEN Haowen

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Abstract:

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 King View 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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Mechanical Characteristics of Flexible Shaft in Flexible Motor Load Transfer

GUO Qiang, ZHANG Delong, YANG Peng, WENG Wei, WU Shuo, JIN Bo

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Abstract:

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 tests to 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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Numerical Simulation Analysis and Optimization of Process Parameters in the Cementing Process of Gas Hydrate-bearing Sediments in Deep Water Oil and Gas Wells

WANG Xiaoyu, ZHENG Mingming, WU Shuang, YAN Shichun, MA Ting, TANG Chengxiang

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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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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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Experimental study on the thermal characteristics of dry drilling of diamond coring bits

SHEN Lina, LI Chun, ZHAO Yi, LIU Hailong, WU Haixia, ZHANG Jianyuan

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Abstract:

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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Research on dual liquid plugging method based on thixotropic slurry

龚浩宇, Ren peigang, Zhang furong, Ma di, Xie bingxi, Fan haijiao

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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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Volume 51,2024 Issue 5

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