Theoretical analysis of pressure-bearing performance on compression packer in low permeability reservoirs

Abstract

Up to date, compression packers have been widely utilized to seal annular space between tubing and casing in the fracturing process of low permeability reservoirs. However, packer end damage under great annulus pressure difference and internal shear failure caused by excessive pressure in tubing are the main failure reasons. Current research works mainly focus on the theoretical model of sealing property with contact stress as evaluation index and less consideration was given to pressure-bearing property in rubber. This paper established a novel analytical model which took into account material properties, geometric dimension and borehole expansion ratio setting the maximum shear stress as evaluation criteria, which can investigate the distribution of shear stress along the axial diameters on compression packer under one end loaded and other end fixed. Also, the accuracy of the analytical model was verified by FEM. Main results illustrated that a) the analytical results can describe the mechanical behavior of the compression process well and the recommended setting pressure was less than 40 MPa; b) with the materials hardened, the compression distance reduced smoothly and the maximum shear stress almost kept unchanged; c) the compression deformation and maximum shear stress rose significantly as the inner diameter of the open hole well increased; d) the height of the packer played a negative role both in maximum compression distance and maximum shear stress of the compression packer.