Oilfield Casing Failure Mechanism Under The Effect Of Soil

The study of casing damage in complex formations is a problem worthy of attention.For some oil fields,the ratio of casing damage in sand and mudstone interlayers is as high as 58.4%.Casing damage in Daqing Oilfield and Jilin Oilfield occurs mostly in sand and shale intervals.Casing damage in creep formations is also a problem for some old oilfields.Casing damage causes huge economic losses.In this paper,sand and mudstone interlayers and creep layer casings are taken as the research objects.The main research work is as follows:(1)The research status of casing damage at home and abroad is summarized.(2)Set up a three-dimensional finite element model of casing-cement-soil to study the mechanical properties of casing in sand-mudstone interlayer environment.The effects of interlayer thickness,casing wall thickness,water injection pressure value and casing ellipticity on casing stress were analyzed.(3)Studying the influence of cement ring properties on the casing stress of sand-mudstone interlayer,and analyzing the effect of cement ring elastic modulus,Poisson’s ratio,thickness and ellipticity on the stress of casing.(4)A two-dimensional finite element model of casing-cement-soil was established,and the stress changes of casing in creep layer under the joint influence of casing ellipticity and cement ring ellipticity were studied.