【作者】 李霄；

【导师】 鞠录岩；

【作者基本信息】 西安石油大学 ， 机械工程（专业学位）， 2025， 硕士

【摘要】 随着长宁A井区页岩气开采的深入,页岩气水平井水力压裂作业中套管变形问题日益突出,截止到2024年,长宁A井区套管变形率为44.8%。因此,深入研究长宁A井区水平井套管变形主要原因至关重要。对长宁A井区的页岩气储层特征、两口典型套管变形井案例、116个水平井套管变形点周围区域地质特征和52口套管变形井基础资料调研统计,分析该井区主要套变类型以及引发套管变形的主要地质因素和工程因素,并通过现场资料分析和数值模拟手段研究长宁A井区页岩气水平井套管变形的主要原因。此外,对取自长宁A井区的页岩岩心进行岩石力学试验和岩石物性参数测定,为后续数值模拟提供具体数据。结果表明,在水力压裂过程中影响水平井套管变形的原因复杂,断层滑移导致套管外挤变形占比最高,为该井区主要套变类型和原因;水平井距断层距离、压裂液排量、断层倾角和储层渗透率等是影响水平井套管变形的主要因素,也是影响断层滑移的主要因素。影响长宁A井区水平井套管变形的主要机理为:水力压裂时断层处孔隙压力升高并改变其应力状态,从而引发断层滑移,最终造成套管变形。通过现场资料分析,确定断层滑移是导致套管变形的主要原因,据此开展以下具体研究。首先,利用有限元法(FEM)建立长宁A井区水力压裂诱发断层滑移的流-固场耦合模型,研究不同压裂因素(水平井距断层距离、压裂液排量、断层倾角和储层渗透率等)对断层滑移的影响。然后,利用FSP断层滑移评判准则,完成不同压裂因素下断层滑移风险评价。结果表明:当压裂液排量相同、井距不同时,水平井距离断层越近,断层滑移的风险显著增加,井距从25m增至75m,滑移风险降低47.8%;当井距相同、压裂液排量不同时,压裂液排量越大,断层越容易出现滑移风险,排量从11m~3/min上升至14m~3/min,滑移风险增加77.8%;断层倾角和储层渗透率的变化则直接影响断层滑移风险程度。其次,利用岩石断裂力学理论公式的断层滑移量计算方法计算出不同压裂因素下断层滑移量。然而在实际工程中,水力压裂作业时断层滑移与套管变形往往同步发生,仅水力压裂诱导断层滑移的数值模拟本身已具有较高复杂性,若将断层滑移与套管变形的同步分析纳入数值模拟,其复杂程度将显著增加。因此本文对该过程数值模拟分析进行简化,即首先分析水力压裂诱导断层滑移的过程,随后探讨断层滑移对套管变形的影响,通过这种分步研究以明确各过程间的关系。在断层滑移导致套管变形数值模拟分析中,首先建立包含断层的储层-水泥环-套管有限元模型,然后以断层滑移量为边界条件,模拟套管变形过程,最后分析出不同压裂因素下套管变形情况。结果表明:相同压裂液排量下,水平井距离断层越近,造成的断层滑移量和套管形变量越大,当井距从25m增至75m时,断层滑移量和套管形变量分别降低51.6mm、16.7mm;相同井距下,压裂液排量越大,断层滑移量和套管形变量也增大,排量从11m~3/min增至14m~3/min,分别增加47.7mm、13.4mm;断层走向与初始最大水平地应力方向夹角为0°且断层倾角为45°、60°、75°时,断层滑移量和套管形变量先增大后减小;储层渗透率增大,断层滑移量和套管形变量随之增大。最后针对长宁A井区套管变形主要原因,提出具体防控建议。本文中水力压裂诱发断层滑移导致套管变形的理论研究结果和防止页岩气水平井套管变形的建议,对解决断层滑移引起套管变形这类工程问题具有重要的理论指导意义。更多还原

【Abstract】 As shale gas extraction in the Changning A well area deepens,the issue of casing deformation in horizontal well hydraulic fracturing operations has become increasingly prominent.By 2024,the casing deformation rate in the Changning A well area had reached44.8%.Therefore,it is critical to conduct in-depth research on the primary causes of casing deformation in horizontal wells in this region.This study examines the shale gas reservoir characteristics of the Changning A well area,two typical casing deformation well cases,the geological features surrounding 116 casing deformation points in horizontal wells,and the basic data from 52 casing deformation wells.The study analyzes the major types of casing deformation in this region,the key geological and engineering factors contributing to casing deformation,and investigates the primary causes of casing deformation in horizontal wells in the Changning A well area through field data analysis and numerical simulation techniques.Additionally,rock mechanics tests and physical property measurements of shale cores from the Changning A well area were performed to provide specific data for subsequent numerical simulations.The results show that the causes of casing deformation during hydraulic fracturing in horizontal wells are complex.Fault slip,which leads to external casing extrusion deformation,accounts for the largest proportion,making it the primary type and cause of casing deformation in this area.The main factors influencing casing deformation in horizontal wells,including horizontal well distance to the fault,fracturing fluid volume,fault dip angle,and reservoir permeability,are also the primary factors influencing fault slip.The main mechanism responsible for casing deformation in horizontal wells in the Changning A well area is the increase in pore pressure at the fault during hydraulic fracturing,which alters the stress state and triggers fault slip,ultimately causing casing deformation.Through field data analysis,fault slip was identified as the primary cause of casing deformation,prompting the following specific studies.First,a fluid-solid coupling model for fault slip induced by hydraulic fracturing in the Changning A well area was established using the Finite Element Method(FEM)to study the effects of different fracturing factors(such as horizontal well distance to the fault,fracturing fluid volume,fault dip angle,and reservoir permeability)on fault slip.Then,using the FSP fault slip judgment criteria,a risk assessment of fault slip under different fracturing conditions was conducted.The results show that,for the same fracturing fluid volume but different well distances,the closer the horizontal well is to the fault,the higher the risk of fault slip.When the well distance increases from 25m to 75m,the slip risk decreases by 47.8%.For the same well distance but different fracturing fluid volumes,an increase in fracturing fluid volume increases the risk of fault slip.When the fluid volume increases from 11m~3/min to 14m~3/min,the slip risk increases by 77.8%.Changes in fault dip angle and reservoir permeability directly influence the degree of fault slip risk.Secondly,the fault slip displacement is calculated using the fault slip formula from rock fracture mechanics under different fracturing factors.However,in actual engineering,fault slip and casing deformation often occur simultaneously during hydraulic fracturing operations.Numerical simulations of fault slip induced by hydraulic fracturing are already highly complex,and incorporating the simultaneous analysis of fault slip and casing deformation would further increase this complexity.Therefore,this study simplifies the numerical simulation analysis by first analyzing the process of fault slip induced by hydraulic fracturing and then exploring the impact of fault slip on casing deformation.This step-by-step approach helps clarify the relationship between the processes.In the numerical simulation analysis of casing deformation caused by fault slip,a finite element model incorporating the fault,reservoir,cement sheath,and casing was first established.Fault slip amounts were used as boundary conditions to simulate the casing deformation process,and casing deformation under different fracturing conditions was then analyzed.The results show that,for the same fracturing fluid volume,the closer the horizontal well is to the fault,the greater the fault slip amount and casing deformation.When the well distance increases from 25m to 75m,the fault slip amount and casing deformation decrease by 51.6mm and 16.7mm,respectively.For the same well distance,an increase in fracturing fluid volume also increases fault slip and casing deformation.When the fluid volume increases from 11m~3/min to 14m~3/min,the fault slip amount and casing deformation increase by47.7mm and 13.4mm,respectively.When the fault strike and the initial maximum horizontal stress direction form an angle of 0°and the fault dip angles are 45°,60°,and 75°,the fault slip amount and casing deformation first increase and then decrease.As the reservoir permeability increases,both fault slip and casing deformation also increase.Finally,specific prevention and control recommendations for casing deformation in the Changning A well area are proposed.The theoretical findings on fault slip-induced casing deformation and the suggestions for preventing casing deformation in shale gas horizontal wells provided in this paper have significant theoretical implications for solving engineering problems related to casing deformation caused by fault slip.更多还原