Abstract: Many oil wells no longer produce because of the fracture of producer casing caused by deformation.This has a great influence over the production of petroleum.This paper points out that, beecause of recover petroleum, the pore-pressure of oil layer is redttced so that the oil layer is compressed.Compressed oil layer gives the casing soiidifieJ in oil layer and additional longitadinal pressure.When oil layer is a tilting strata, besides the longitudinal pressure acting on casing, the casing is also acted on by a couple of transversal shearing forces.It is a probable explanation that compression of oil layer leads to the casiug deformation.