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International Petroleum and Petrochemical technology Conference 2024, IPPTC 2024

作者： Sun, Yuqi Liu, Li Hui, Chengyu Zhang, Yiqun Ji, Guodong CNPC Engineering Technology R&D Company Limited China College of Safety and Ocean Engineering China University of Petroleum Beijing China State Key Laboratory of Natural Gas Hydrate China University of Petroleum Beijing China

As a clean energy source, natural gas hydrate resources are essential to the development of energy in the twenty-first century. However, the degree of consolidation of the hydrate reservoir is low, and complex accidents such as wellbore instability, reservoir collapse, and gas production leakage will be caused if improperly exploited. The laboratory employs a self-developed triaxial shear test equipment that operates under high pressure and low temperature conditions. This equipment is specifically designed to determine the mechanical parameters and strength characteristics of methane hydrate bearing sediment (MHBS) samples. It is used to create water-saturated hydrate deposits with varying levels of saturation. The synthesis of MHBS samples with varying saturations is achieved by precisely regulating the amount of water. The saturation of MHBS is then determined and confirmed by the utilization of the "water content method" and the "gas collection method." Triaxial shear tests are conducted on MHBS to examine the impact of hydrate saturation on the mechanical parameters and strength behaviours of MHBS. The experimental findings demonstrate that the presence of hydrate crystals enhances the robustness of the depositing medium. The stress-strain curves of MHBS have a hyperbolic shape, indicating strain hardening features. The stress-strain curves may be categorized into three distinct stages: the initial elastic deformation, followed by a slow shift to the initial yield deformation, and ultimately leading to strain hardening. As axial strain rises, the behaviour of the MHBS transitions progressively from elastic deformation to plastic deformation. The shear strength and initial yield strength of MHBS enhance with higher hydrate saturation. The reason for this is that as the hydrate saturation rises, the influence of hydrate crystals on the enhancement of sediment strength becomes more pronounced. However, the initial yield strain of each MHBS sample is between 0.5% a

关键词： Shear strength

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Study On Shear & Tensile Activation Of Hydraulic Fracturing In Natural Fractured reservoirs

Study On Shear & Tensile Activation Of Hydraulic Fracturing ...

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2023 SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition, APOG 2023

作者： Zhang, Yang Qiao, Yan Zhou, Fujian ren, dengfeng Liu, Yuzhang Bai, Jie China University of Petroleum Beijing China CNPC Engineering Technology R&D Company Limited China PetroChina Tarim Oilfield Company China Research Institute of Petroleum Exploration & Development China

ISBN: (纸本)9781613999813

The most fundamental purpose of reservoir stimulation is to maximize stimulation volume. For reservoirs developed with natural fractures, the maximization of fracture activation (tensile & shear activation) area should be pursued. Many scholars have studied the mechanical conditions of natural fractures activation, and used stress shadow to optimize cluster spacing. However, there is a lack of in-depth research on fracture propagation law, relationship between fracture activation and stress shadow, and factors affecting natural fracture activation. In this paper, numerical simulation methods are used to establish a true three-dimensional hydraulic fracturing model for reservoirs with natural fractures, and the quantitative evaluation indicators of stress shadow area and activation degree of natural fractures are formed. By studying the effects of different natural fracture properties, mechanical and engineering parameters on fracture propagation, stress shadow and natural fracture activation, the main controlling factors affecting fracture propagation and turning, the relationship between fracture activation and stress shadow, and changing rules of fracture activation are clarified. Finally, the fracture turning and accuracy of model are verified by microseismic monitoring data. Studies have shown that large-scale, high-density natural fractures, high net pressure, low in-situ stress difference, and moderate stress-fracture angle (30°~60°) can easily divert the propagation of hydraulic fractures instead of expanding in the horizontal maximum principal stress (Shmax) direction. Fracture tensile activation has a strong positive correlation with stress shadow area, that is, tensile activation leads to the increase of stress shadow area, while fracture shear activation has almost no correlation. Fracture tensile & shear activation area is in a competitive relationship, and shear fractures are dominant when the stressfracture angle is 45-60°, the in-situ stress differenc

关键词： Stresses

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Numerical Simulation research on Seal Failure of remedial Cement Sheath in Oil and Gas Wells 28th

Numerical Simulation Research on Seal Failure of Remedial Ce...

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28th International Conference on Computational and Experimental engineering and Sciences, ICCES 2022

作者： Jiang, Jiwei Chen, Zhixue Hao, Weiwei Li, Jun Xi, Yan Zhai, Wenbao Chen, Xuefeng Li, Bo CNPC Engineering Technology R&D Company Limited Beijing102206 China China University of Petroleum-Beijing Beijing102249 China Beijing University of Technology Beijing100124 China

ISBN: (纸本)9783031020964

due to insufficient cement return height during cementing operations, there may be a channel for oil and gas leakage between the wellbore and the formation, causing environmental problems such as groundwater pollution. Therefore, it is necessary to reinject the cement slurry into the original wellbore annulus and evaluate the sealing performance of the remedial cement sheath. However, the current theoretical and applied research on this aspect is relatively lacking. In response to this, a new model for calculating elastoplastic strain of the remedial cement sheath/original cement sheath based on damage mechanics was established, and the plastic deformation behavior of the interface area was studied. The seal failure mechanism of the wellbore remedial cement sheath is clarified, and the influence of the mechanical parameters of the remedial cement sheath on the cumulative plastic strain and the micro-annulus of the remedial cement sheath-casing interface is analyzed. The results show that under the combined action of the internal pressure of the casing and the non-uniform ground stress, the cumulative plastic deformation of the inner wall of the remedial cement sheath and the micro-annular gap at the interface are the main reasons for the sealing failure of the remedial cement sheath. Increasing the Poisson’s ratio, cohesion strength and internal friction angle of the remedial cement sheath and reducing the elastic modulus of the remedial cement sheath, is helpful to reduce the accumulated plastic strain and improve the sealing performance of the remedial cement sheath. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Cements

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A Novel Method for real-time Identification of Formation Lithology Based on Machine Learning 56

A Novel Method for Real-time Identification of Formation Lit...

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56th U.S. rock Mechanics/Geomechanics Symposium

作者： Yao, Xuezhe Song, Xianzhi Han, Liang Wang, Zheng Zhang, rui Liu, Wei Fu, Jiasheng Zhu, Shuo Zhu, Zhaopeng China University of Petroleum Beijing China CNPC Engineering Technology R&D Company Limited Beijing China

ISBN: (纸本)9780979497575

real-time identification of formation lithology is of great significance to optimization of drilling rate and directional drilling. However, the experimental observation method and the statistical analysis method require researchers with rich experience and professional knowledge, and the identification efficiency is low and the cost is high. The goal of this study is to employ machine learning for identifying lithology from only the real-time drilling parameters without any downhole measurements. First, the real-time drilling data were cleaned, and then the correlation between each drilling parameter and formation lithology was analyzed by correlation analysis algorithm, and 13 drilling parameters were selected as model inputs. And then random forest (rF) and XGBoost algorithms are used to develop lithology identification models respectively. The results show that the XGBoost model has the best result in identifying formation lithology, with an accuracy of 79.21%. Finally, feature importance analysis shown that MWI, MWO and MFI have important effects on model performance. This study has important implications for improving the probability of drilling into reservoirs and reducing drilling costs. © 2022 ArMA, American rock Mechanics Association.

关键词： Lithology

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A New Magnetic ranging technology Achieves the Accuracy and Operational Flexibility Needed for Plugging Complex Old Wells of Underground Gas Storage 12th

A New Magnetic Ranging Technology Achieves the Accuracy and ...

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12th International Field Exploration and development Conference, IFEdC 2022

作者： Che, Yang Qiao, Lei Yuan, Guang-Jie Lin, Sheng-Jie du, Wei-Qiang Wang, Chen-Long Zhu, Xiao-Yu CNPC Engineering Technology R&D Company Limited Beijing China National Engineering Research Center for Oil & Gas Drilling and Completion Technology Beijing China North East Petroleum University Daqing China

ISBN: (纸本)9789819919635

Using depleted gas fields to store natural gas is one of the most common underground gas storage (UGS) all over the world. However, many abandoned wells with complex conditions such as downhole fishes or broken casings affect the sealing property of UGS. Thus, it is essential to plug these wells that minimize the risk of leakage. But traditional inclinometer technology is challenging to meet the measurement accuracy due to the cumulative error. A new method based on magnetic ranging technology has been developed and successfully applied in the UGS project to overcome the problem of plugging complex wells. The main technical idea is to drill a new well called relief well around the target well. Then, the electromagnetic wave is excited to the formation, and the magnetic signal generated by the electromagnetic wave will be gathered in the target well at the same time. due to the different conductivity, most of the signals will gather along the ferromagnetic string of the target well. Next, the array gradiometer of the magnetic ranging tool will receive the corresponding magnetic signals. Through accurate calculation, the relative position (distance and direction) between the two wells is given. According to the relative position measurement, the BHA (Bottom Hole Assembly) is used to drill forward repeatedly until the new well connects to the target well completely. Meanwhile, error model and geology-engineering integration are also considered to obtain the target spot and its TVd (true vertical depth). The magnetic ranging technology has several advantages, including lower cost and lower risk for the operator. Theoretically, various laboratory tests were conducted to demonstrate the ability to provide reliable and accurate ranging data for relatively good positioning. Practically, the paper presents field trials exclusively with three typical complex wells of UGS to validate the proposed concept. The results of laboratory tests show excellent agreement on position mea

关键词： Gas industry

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Experiment on Mechanical Properties and Seepage Capability of deep Tight Sandstone under True-Triaxial Stresses Environment

Experiment on Mechanical Properties and Seepage Capability o...

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2021 Abu dhabi International Petroleum Exhibition and Conference, AdIP 2021

作者： Li, Jiaying Qi, Chunyan Gu, Ye Ye, Yu Zhao, Jie CNPC Engineering Technology R&D Company Limited CNPC Tarim Oilfield Company

ISBN: (纸本)9781613998342

The characteristics of seepage capability and rock strain during reservoir depletion are important for reservoir recovery, which would significantly influence production strategy optimization. The Cretaceous deep natural gas reservoirs in Keshen Gasfield in Tarim Basin are mainly buried over 5000 m, featuring with ultra-low permeability, developed natural fractures and complex in-situ stress states. However, there is no comprehensive study on the variation of mechanical properties and seepage capability of this gas reservoir under in-situ stress conditions and most studies on stress-sensitivity are conducted under conventional triaxial or uniaxial stress conditions, which cannot truly represent in-situ stress environment. In this work, Cretaceous tight sandstone in Keshen Gasfield was tested under true-triaxial stresses conditions by an advanced geophysical imaging true-triaxial testing system to study the stress-sensitivity and anisotropy of rock stress-strain behavior, porosity and permeability. Four groups of sandstone samples are prepared as the size of 80mm×80mm×80mm, three of which are artificially fractured with different angle (0°,15°，30°) to simulate hydraulic fracturing. The test results corresponding to different samples are compared to further reveal the influence of the fracture angle on rock mechanical properties and seepage capability. The samples are in elastic strain during reservoir depletion, showing an apparent correlation with fracture angles. The porosity decreases linearly with stress loading, where the decrease rate of effective porosity of fracture samples is significantly higher than that of intact samples. The permeabilities decrease exponentially and show significant anisotropy in different principal stress directions, especially in σH direction. The mechanical properties and seepage capability of deep tight sandstone are successfully tested under true-triaxial stresses conditions in this work, which reveals the stress-sensitivity of anis

关键词： Porosity

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research on Cement Sheath Integrity Under High Temperature during In-Situ development for Shale Oil Well 28th

Research on Cement Sheath Integrity Under High Temperature D...

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28th International Conference on Computational and Experimental engineering and Sciences, ICCES 2022

作者： Guo, Xueli Qi, Fengzhong Yu, Yongjin Jin, Jianzhou Guo, Yuchao Ji, Hongfei Cheng, Yongqin Zhao, Zhengyang CNPC Engineering Technology R&D Company Limited Beijing China Research Institute of Petroleum Exploration and Development Beijing China China University of Petroleum Beijing China

ISBN: (纸本)9783031020964

The temperature is as high as 500 °C at the bottom of shale oil wells during in-situ development. during shale oil production, the fluids with high temperature are transmitted to the wellhead, and the wellbore temperature will rise extremely, which greatly affects the cement sheath integrity. In this paper, the linear expansion coefficient of cement stone under the temperature of 500 ℃ were measured. Based on the experimental data and the field data of shale oil well, the stage finite element modeling method was adopted to establish a casing-cement-formation (CCF) model considering the temperature and pressure coupling. The results revealed that the linear expansion coefficient of cement stone decreases linearly with the increase of temperature. When the temperature was less than 250 ℃, the cement stone expanded. However, when the temperature exceeded 250 ℃, it shrank. The maximum shrinkage ratio can be 25 × 10–6/℃ for the temperature of 500 ℃. The circumferential stress of the inner wall of cement sheath first increased rapidly, then slowly decreased to be stable. The larger the cement stone shrink ratio was, the greater the circumferential stress was. The maximum circumferential stress can exceed 10 MPa for the shrink ratio of 25 × 10–6/℃. It can be concluded that the circumferential stress appears in a tensile state under high temperature conditions, which can easily lead to the failure of the cement sheath seal. The strength of the cement stone should be considered when designing the cement slurry property. In addition to the decay performance, the expansion of the cement stone should also be designed to ensure that the cement stone does not shrink when subjected to high temperature conditions. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Cements

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Study on the research Progress and development Trend of refracturing Technique in Shale Gas reservoirs 11th

Study on the Research Progress and Development Trend of Refr...

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11th International Field Exploration and development Conference, IFEdC 2021

作者： Zhou, Yi Yang, Yi Yu, Yong-liang Hu, Xi-hui Guo, Jian-hua Zhu, Ying-jie Wang, Jian-li Yin, Hong-wei CNPC Engineering Technology R&D Company Limited Beijing China Southwest Oil and Gas Field Company of PetroChina Chengdu China

ISBN: (纸本)9789811921483

refracturing technique is a promising means to improve the output and estimated ultimate recovery of shale oil and gas resources, which is an efficient method to recover the productivity of low permeability old wells either. refracturing technique has achieved good results in the development of shale gas wells in North America, which increase the output and decrease the extraction cost significantly of shale gas resources. It is also necessary to improve development efficiency in shale gas of China using the refracturing technique on account of that the defects of unstable and large attenuation of the production are exposed with the further development of shale oil and gas resources in China. The principle and characteristics of refracturing technique are elaborated in this paper. The research progress of refracturing technique is introduced and the theories and applications of conventional refracturing methods like mechanical steering, chemical steering and fiber steering are discussed. The development trend of refracturing technology is also analyzed and the difference on merits and demerits between conventional refracturing methods and advanced methods like the wellbore reconstruction method based on expandable tubular are compared. The conclusions obtained in this paper can provide a theoretical reference for the development of refracturing technique and could provide a technical support for cost decreasing and benefit increasing for the exploration of shale oil and gas resources in China. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Shale gas

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Studies on Lost Circulation risk of deep Shale Formation Based on Fracture Prediction and rock Mechanical Properties 56

Studies on Lost Circulation Risk of Deep Shale Formation Bas...

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56th U.S. rock Mechanics/Geomechanics Symposium

作者： Wen, Bo Wang, Yuan Chen, Gang Zhang, Peiyu Guo, Kaijie Fu, Li Feng, Ming Yang, Henglin Zhong, Chengxu PetroChina Southwest Oil&Gasfield Company Chengdu China CNPC Engineering Technology R&D Company Limited Beijing China

ISBN: (纸本)9780979497575

Lost circulation is a technical problem in drilling engineering, resulting in increased drilling cost and extended drilling cycle. reservoir rocks in Block A of Shale Gas have the characteristics of low porosity and low permeability, strong heterogeneity and fault fracture development. Lost circulation is mainly caused by fracture. Seismic fracture prediction to assess lost circulation risk has limitations. Therefore, it is necessary to study more effective methods of lost circulation risk assessment. In this paper, based on the analysis of lost circulation, seismic prediction on fractures and rock mechanics parameters in block A, a comprehensive evaluation method of lost circulation index is formed by using seismic prediction of the relative degree of fracture development, fracture apparent length and the combination of Young's modulus and Poisson's ratio in 3d attribute modeling, and the classification evaluation standard is established. The method is used to evaluate the lost circulation risk of completion drilling in shale gas well of Block A, and the evaluation results are consistent with the well drilling data. Lost circulation index evaluation method can effectively evaluate the risk of lost circulation in shale formation with low porosity and low permeability, strong heterogeneity and fracture development, which can promote the efficient development of shale gas. © 2022 ArMA, American rock Mechanics Association.

关键词： Forecasting

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Insights into the carbonate/bicarbonate ion-induced failure mechanism of bentonite in drilling fluids

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Journal of Molecular Liquids 2025年 417卷

作者： deng, Xuefei Lv, Kaihe Qiao, Huotong Li, Jian Sun, Jinsheng Huang, Ning Fan, Junhao Liao, Ting Qingdao266580 China CNPC Engineering Technology R&D Company Limited Beijing102200 China Engineering Technology Department of CNPC Chuanqing Drilling Engineering Co. Ltd. Chengdu610000 China

during deep oil and gas drilling, drilling fluids are often polluted with carbon dioxide (CO2). The intrusion of CO2 can affect bentonite performance, leading to deterioration or even failure of drilling fluids. To further investigate the influence of CO2 pollution on the bentonite and its failure mechanism, Na2CO3 simulation experiments were conducted. Performance evaluation showed that as the concentration of HCO3− and CO32− increased, the viscosity, filtration loss, and mud cake permeability of drilling fluids significantly increased. Meanwhile, the drilling fluid foaming was particularly evident. Mechanism studies indicated that the adsorption of HCO3− and CO32− on the bentonite diminished the electrostatic interactions and interlayer spacing between particles, leading to the particles aggregation and a decrease in Zeta potential, ultimately causing the hydration film on the bentonite to become thinner. Simultaneously, this also led to a decline in the dispersibility of bentonite. This study can offer a new research thread for the failure mechanism of bentonite under CO2 pollution and indicate the direction for the study of drilling fluid resistance to acidic gas pollution. © 2024 Elsevier B.V.

关键词： drilling fluids

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