Experiment and simulation on the integrity of cement ring interface in deep water shallow formation

Abstract

The integrity of cement ring interface is critical for the safe production of crude oil and nature gas and the protection of marine environment in deep water shallow formation. Due to the slow hydration speed of the cement under low temperature and the low compaction of the weakly consolidated formation, the casing-cement-formation interfaces are prone to generate micro-annulus. In this paper, a device for testing the interface radial bond strength was designed. The test results showed that the cement-casing interface radial bond strength gradually increased with the increase of curing temperature, and the cement-formation interface radial bond strength increased with the decrease of water content in the formation. Based on ABAQUS finite element software, the tensile stress on the cement-casing interface during the reduction of casing internal pressure, and the tensile stress on the cement-formation interface during the hardening and shrinking process of cement were studied. When the casing internal pressure reduced, the hardened cement with high elastic modulus generated greater tensile stress on the cement-casing interface. The casing internal pressure reduction should not exceed 2.49, 2.75 and 5.41 MPa at the formation temperature of 4, 7 and 10 °C, respectively. In addition, the cement slurry used in this paper can be well bonded with the weakly consolidated formation in deep water shallow formation. This paper is of great significance to study the failure mechanism of cement ring interface integrity in deep water shallow formation, and has guidance for proposing corresponding rationalization suggestions and measures.