Study On Casing Safety Evaluation Method Under Large-scale Fracturing Condition

Horizontal well is one of the advanced well types for the development of unconventional oil and gas resources.The development and application of horizontal well technology is very important for the efficient development of tight sandstone gas reservoirs.Volumetric fracturing is characterized by large scale and high operating pressure.Large-scale volumetric fracturing after cementing often results in changes in casing behavior that may not have been taken into account in casing design.Therefore,high strength construction is likely to cause serious damage to casing.It is very important to analyze the stress and deformation of casing in horizontal section of sandstone horizontal well for preventing casing loss.In this paper,the numerical simulation method is used to study the force of casing as follows:(1)Through a large number of literature research,the causes and forms of casing damage are analyzed from two aspects of geological factors and engineering factors.The geological factors such as rock stress and fault activity around the well are carefully analyzed,and the influence of engineering factors such as casing quality and fracturing on casing is also analyzed.(2)The finite element software ABAQUS was used to simulate the influence of different factors that may be encountered in the fracturing process on casing stress.The influences of elastic modulus of formation,in-situ stress redistribution,pressure and temperature stress in casing on casing stress are obtained respectively.(3)Using the finite element software ABAQUS,the influence law of cement ring material and dimensional parameters on casing extrusion resistance was obtained.Focusing on the finite element simulation of the missing cement ring,the stress law of casing with single notch and multi-notch with different missing degree was analyzed and obtained.(4)PFC2D discrete element software was used to simulate and obtain the influence rules of different fracture forms on casing stress and deformation under uneven in-situ stress from three aspects of fracture length,fracture Angle and fracture density.