Study On Strength Of Casing In Horizontal Well Safety Evaluation Considering Rock Mechanical Parameter

Oil field casings are often damaged by the variation of the rock mechanical parameters during production and injection.Casing damage can cause system instability and reservoir damage that even lead to accidents such as that unable to be exploited.It serious effects on the formal oil and gas production and caused enormous losses in economy.According to the study of failure casing in oil and gas field and analysis the causes of the accidents is the variation of the rock mechanical parameters.It is that pore pressure would be changed during production and injection that would effect on the mechanical property of reservoir rocks.It will threaten the security of casing eventually.For the analysis of the influence of the water content on constitution relation and strength of shales,the paper studies water-sensitive shale that initiatively adds the stress increment which caused by the variations of water content to the original constitutive equations.Also,it completes the types of stress increments of rock-like materials and gets the progressive constitutive theory of water-sensitive shale.It is conducted to the original constitutive equations improve accuracy of on the influence of the water content on strength of rock and optimization model of surrounding rock.It is that formation pressure transmit to casing with passing cement sheath.So the different materials and size of cement sheath and casing would lead to the variation of pressure subjected by casing.It is particularly important to comprehensive consideration that coupling effect of the system are composed of casing,cement sheath and surrounding rock.Through a number of basic assumptions make the analysis result and realities have varied widely in individual casing assumptions.The paper studies the system are composed of casing,cement sheath and surrounding rock that comprehensive consider the effect on casing strength and lays the foundation for optimizing the system are composed of casing,cement sheath and surrounding rock.Through heterogeneous materials and instability of compression strength of rock.It is difficult to analyses the rock effects on the system are composed of casing and cement sheath.So it is based on the system are composed of casing,cement sheath and surrounding rock for analysis casing strength of horizontal well.The paper studies the system are composed ofcasing,cement sheath and surrounding rock under actual conditions.Finite element simulation is carried out by ANSYS in order to analyses the variation of water content effect on the system are composed of casing,cement sheath and surrounding rock.Its intention is to provide guidance suggestions for selection of casing under complicated geological conditions in horizontal well.