Study on Rubber Seal Design of a Swellpacker in Oil Well Cementing

Abstract

A swellpacker has the advantages of high isolation reliability and good gas migration resistance in open holes. This paper analyzed the contact pressure and stress distribution of the downhole swellpacker, and optimized rubber structure for various formations. 1) The research shows that thermal expansion can better explain the expanding process of the rubber after adsorption of oil. 2) The maximum contact pressure occurs in the middle of rubber, and the sealing effect of the packer increases exponentially with the length and thickness of rubber. 3) The shear stress model established for various formations indicates that the shear stress increases linearly with the contact pressure. According to the formation nature in northeastern Sichuan of China, 4) the optimum swellpacker rubber should be 18 mm in thickness, and 1.173 m in length for sandstone formation, 1.402 m for shale formation and 1.415 m for mudstone formation. 5) Stress verification reveals that the rubber does not fail and can work safely in downhole.