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Finite element analysis for wellbore stability of transversely isotropic rock with hydraulic-mechanical-damage coupling

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Science China(Technological Sciences) 2017年第1期60卷 133-145页

作者： WANG YongLiang LIUZhanLi YANG HengLin ZHUANG Zhuo Drilling Research Institute China National Petroleum Corporation Beijing 100195 China

The finite element analysis （FEA） technology by hydraulic-mechanical-damage （HMD） coupling is proposed in this paper for wellbore stability analysis of transversely isotropic rock, developed basing on the recently established FEA technology for iso- tropic rock. The finite element （FE） solutions of numerical wellbore model, damage tensor calculation and Pariseau strength criterion for transversely isotropic rock are developed for researching the wellbore failure characteristics and computing the collapse and fracture pressure of laminated rock as shale reservoirs. The classic Blot constitutive for rock as porous medium is introduced to establish a set of FE equations coupling with elastic solid deformation and seepage flow. To be in accord with the inclined wellbore situation, the coordinate transformation for global, wellbore, in-situ stress and transversely isotropic for- mation coordinate systems is established for describing the in-situ stress field and the results in laminated rock. To be in accord with the practical situation, a three-dimensional FIE model is developed, in which several other auxiliary technologies are com- prehensively utilized, e.g., the typical Weibull distribution function for heterogeneous material description and adaptive tech- nology for mesh refinement. The damage tensor calculation technology for transversely isotropic rock are realized from the well-developed continuum damage variable of isotropic rock. The rock is subsequently developed into a novel conceptual and practical model considering the stress and permeability with the damage. The proposed method utilizing Parisean strength cri- terion fully reflects the strength parameters parallel or perpendicular to bedding of the transversely isotropic rock. To this end, an effective and reliable numerically three-step FEA strategy is well established. Numerical examples are given to show that the proposed method can establish efficient and applicable FE model and be suitable for analyz

关键词： finite element analysis wellbore stability transversely isotropic rock damage tensor hydraulic-mechanical-damagecoupling

Effects of creep characteristics of natural gas hydrate-bearing sediments on wellbore stability

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Petroleum Science 2022年第1期19卷 220-233页

作者： Yang Li Yuan-Fang Cheng Chuan-Liang Yan Zhi-Yuan Wang Li-Fang Song School of Petroleum Engineering China University of Petroleum(East China)66 West Changjiang RoadHuangdao DistrictQingdao 266000China

Natural gas hydrate(NGH)reservoirs consist of the types of sediments with weak cementation,low strength,high plasticity,and high *** on the kinetics and thermodynamic characteristics of NGH decomposition,herein a heat-fluid-solid coupling model was established for studying the wellbore stability in an NGH-bearing formation to analyze the effects of the creep characteristics of NGH-bearing sediments during long-term *** results demonstrated that the creep characteristics of sediments resulted in larger plastic yield range,thus aggravating the plastic strain accumulation around the ***,the creep characteristics of NGH-bearing sediments could enhance the effects induced by the difference in horizontal in situ stress,as a result,the plastic strain in the formation around the wellbore increased nonlinearly with increasing difference in in situ *** lower the pore pressure,the greater the stress concentration effects and the higher the plastic strain at the ***,the lower the initial NGH saturation,the greater the initial plastic strain and yield range and the higher the equivalent creep *** plastic strain at the wellbore increased nonlinearly with decreasing initial saturation.

关键词： Natural gas hydrates wellbore stability Creep Plastic yield

Finite element analysis for inclined wellbore stability of transversely iso-tropic rock with HMCD coupling based on weak plane strength criterion

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Science China(Technological Sciences) 2017年第4期60卷 624-637页

作者： WANG YongLiang ZHUANG Zhuo LIU ZhanLi YANG HengLin LI ChenFeng Applied Mechanics Laboratory School of Aerospace Engineering Tsinghua University Zienkiewicz Centre for Computational Engineering & Energy Safety Research Institute College of Engineering Swansea University Drilling Research Institute China National Petroleum Corporation

The finite element analysis(FEA) technology by hydraulic-mechanical-chemical-damage(HMCD) coupling is proposed in this paper for inclined wellbore stability analysis of water-sensitive and laminated rock, developed basing on the recently established FEA technology for transversely isotropic rock with hydraulic-mechanical-damage(HMD) coupling. The chemical activity of the drilling fluid is considered as phenomenological hydration behavior, the moisture content and parameters of rock considering hydration could be determined with time. The finite element(FE) solutions of numerical wellbore model considering the chemical activity of drilling fluid, damage tensor calculation and weak plane strength criterion for transversely isotropic rock are developed for researching the wellbore failure characteristics and computing the time-dependent collapse and fracture pressure of laminated rock as shale reservoirs. A three-dimensional FE model and elastic solid deformation and seepage flow coupled equations are developed, and the damage tensor calculation technology for transversely isotropic rock are realized by introducing effect of the hydration and the stress state under the current load. The proposed method utilizing weak plane strength criterion fully reflects the strength parameters in rock matrix and weak plane. To the end, an effective and reliable numerically three-step FEA strategy is well established for wellbore stability analysis. Numerical examples are given to show that the proposed method can establish efficient and applicable FE model and be suitable for analyzing the timedependsolutions of pore pressure and stresses, and the evolution region considering the hydration surrounding wellbore,furthermore to compute the collapse cycling time and the safe mud weight for collapse and fracture pressure of transversely isotropic rock.

关键词： finite element analysis wellbore stability transversely isotropic rock hydraulic-mechanical-chemical-damage coupling weak plane strength criterion

Finite Element Method Simulation of wellbore stability under Different Operating and Geomechanical Conditions

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Fluid Dynamics & Materials Processing 2024年第1期20卷 205-218页

作者： Junyan Liu Ju Liu Yan Wang Shuang Liu Qiao Wang Yihe Du Oil&Gas Project Research Institute PetroChina Tarim Oilfield CompanyKorla841000China Petroleum Engineering School Southwest Petroleum UniversityChengdu610500China

The variation of the principal stress of formations with the working and geo-mechanical conditions can trigger wellbore instabilities and adversely affect the well completion.A finite element model,based on the theory of poro-elasticity and the Mohr-Coulomb rock damage criterion,is used here to analyze such a *** changes in wellbore stability before and after reservoir acidification are simulated for different pressure *** results indicate that the risk of wellbore instability grows with an increase in the production-pressure difference regardless of whether acidification is completed or not;the same is true for the instability *** acidizing,the changes in the main geomechanical parameters(i.e.,elastic modulus,Poisson’s ratio,and rock strength)cause the maximum wellbore instability coefficient to increase.

关键词： wellbore stability finite element acidizing operation well completion

Investigation on influence of drilling unloading on wellbore stability in clay shale formation

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Petroleum Science 2020年第3期17卷 781-796页

作者： Yi Ding Xiang-Jun Liu Ping-Ya Luo State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu 610500SichuanPeople's Republic of China Deep Earth Energy Lab Department of Civil EngineeringMonash UniversityMelbourne 3800Australia

wellbore collapse frequently happens in the clay shale *** maintain wellbore stability,appropriate mud pressure is a vital *** clay formation is opened,drilling unloading occurs,modifying rock structure and strength at the wall of borehole,which affects the selection of mud ***,mechanism of drilling unloading is still poorly understood which in return will bring a concern to wellbore ***,in this study,a combination of triaxial compressive test and ultrasonic wave test has been used to simulate drilling unloading and analyze its *** indicate that more void space is created inside the clay shale sample due to *** structure change leads to a decline of strength and acoustic ***,unloading influence is depended on varying drilling unloading *** unloading range and fast unloading rate are able to enhance *** various degrees of unloading impact,collapse pressure equivalent density has a clear modification,proving that unloading is a non-negligible influencing factor of wellbore ***,the unloading effect is much stronger in large confining pressure,implying that more attention should be given to unloading when drilling is in extreme deep or high geostress *** in this paper can offer theoretical guidance for drilling in the clay shale formation.

关键词： Drilling unloading Clay shale wellbore stability Rock strength

Geomechanical analysis of an oil field:Numerical study of wellbore stability and reservoir subsidence

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Petroleum Research 2023年第3期8卷 350-359页

作者： Saeed Shad Parvin Kolahkaj Davood Zivar Department of Chemical and Petroleum Engineering Sharif University of TechnologyTehranIran PanTerra Geoconsultants B.V LeiderdorpNetherlands

Geomechanics as the knowledge of rock deformation and stability is an indispensable part of all field development *** geomechanical analyses leads to a safer and more efficient operation otherwise different kinds of instability and distortion might *** this study,the geomechanical behavior of Ilam and Sarvak formations of an oil field in southwest of Iran was *** research objectives can be summarized as wellbore stability evaluation and predicting the value of reservoir subsidence due to pressure drop as a result of reservoir fluid *** fulfill these,a set of petrophysical logs run in the exploration well of this green field were ***,using empirical correlations and statistical methods,required data for evaluating wellbore stability during drilling,specifying safe mud window to discover reservoir breakdown pressure,predicting the possibility of wellbore collapse in field lifetime,and assessing reservoir subsidence were *** results revealed that the average subsidence value as the consequence of production within 21 years is 0.275 ft Which is not *** terms of wellbore stability,it was concluded that all horizontal and vertical wells remain stable during this time *** to conclude,field development is not associated with alarming incidents from geomechanical aspect.

关键词： Dynamic geomechanical properties Subsidence Formation compaction wellbore stability Stress streonet

The influence of water-based drilling fluid on mechanical property of shale and the wellbore stability

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Petroleum 2016年第1期2卷 61-66页

作者： Shu He Lixi Liang Yinjin Zeng Yi Ding Yongxue Lin Xiangjun Liu Sinopec Research Institute of Petroleum Engineering Beijing 100101China State Key Lab of Oil&Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengduSichuan 610500China

Because of high cost and pollution of oil-based drilling fluid,the water-based drilling fluid is increasingly used ***,bedding planes and micro-cracks are rich in shale *** water-based drilling fluid contacts formation rock,it causes the propagation of crack and invasion of drilling fluid,which decrease shale strength and cause wellbore *** this paper,we analyzed influence of water-based drilling fluid on shale strength and failure mode by mechanics *** on those experimental results,considering the effect of bedding plane and drilling time,we established modeling of wellbore stability for shale *** result from this model indicates that in certain azimuth of horizontal well,collapsing pressure increases dramatically due to shale failure along with bedding *** drilling operation,those azimuths are supposed to be *** model is applicable for predication of collapsing pressure in shale formation and offers reference for choosing suitable mud weight.

关键词： Water-based drilling fluid Shale Bedding plane wellbore stability

wellbore stability model in shale formation under the synergistic effect of stress unloading-hydration

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Petroleum Exploration and Development 2023年第6期50卷 1478-1486页

作者： DING Yi LIU Xiangjun LIANG Lixi XIONG Jian LI Wei WEI Xiaochen DUAN Xi HOU Lianlang State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu 610500China School of Geoscience and Technology Southwest Petroleum UniversityChengdu 610500China School of Science Southwest Petroleum UniversityChengdu 610500China

According to the transversely isotropic theory and weak plane criterion, and considering the mechanical damages due to stress unloading and hydration during drilling, a shale wellbore stability model with the influence of stress unloading and hydration was established using triaxial test and shear test. Then, factors influencing the wellbore stability in shale were analyzed. The results indicate that stress unloading occurs during drilling in shale. The larger the confining pressure and axial stress, the more remarkable weakening of shale strength caused by stress unloading. The stress unloading range is positively correlated with the weakening degree of shale strength. Shale with a higher development degree of bedding is more prone to damage along bedding. In this case, during stress unloading, the synergistic effect of weak structural plane and stress unloading happens, leading to a higher weakening degree of shale strength and poorer mechanical stability, which brings a higher risk of wellbore instability. Fluid tends to invade shale through bedding, promoting the shale hydration. Hydration also can weaken shale mechanical stability, causing the decline of wellbore stability. Influence of stress unloading on collapse pressure of shale mainly occurs at the early stage of drilling, while the influence of hydration on wellbore stability mainly happens at the late stage of drilling. Bedding, stress unloading and hydration jointly affect the wellbore stability in shale. The presented shale wellbore stability model with the influence of stress unloading and hydration considers the influences of the three factors. Field application demonstrates that the prediction results of the model agree with the actual drilling results, verifying the reliability of the model.

关键词： shale drilling bedding stress unloading hydration shale strength wellbore stability

A review of the shale wellbore stability mechanism based on mechanicalechemical coupling theories

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Petroleum 2015年第2期1卷 91-96页

作者： Qiangui Zhang Wenyu Jia Xiangyu Fan Yongchang Liang Yang Yang State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengduSichuan 610500China School of Oil&Natural Gas Engineering Southwest Petroleum UniversityChengduSichuan 610500China School of Geoscience and Technology Southwest Petroleum UniversityChengduSichuan 610500China

wellbore instability in hard brittle shale is a critical topic related to the effective exploitation of shale gas *** review first introduces the physicalechemical coupling theories applied in shale wellbore stability research,including total water absorption method,equivalent pore pressure method,elasticity incremental method of total water potential and non-equilibrium thermodynamic ***,the influences of water activity,membrane efficiency,clay content and drilling fluid on shale wellbore instability are *** demonstrate that shale and drilling fluid interactions can be the critical factors affecting shale wellbore *** effects of thermodynamics and electrochemistry may also be considered in the future,especially the microscopic reaction of shale and drilling fluid *** example of this reaction is the chemical reaction between shale components and drilling fluid.

关键词： Petroleum engineering Shale wellbore stability Mechanicalechemical coupling Instability mechanism