Experimental Study on Failure Mechanism of Casing Under the Synergy of Temperature and Internal Pressure

Abstract

In recent years, the gas wells with high pressure, high temperature, and high H2S are increasing gradually, but the burst of casing and tubing in these wells will cause the gas channeling and overflow, and the gas with H2S flows up to surface, which causes huge damage. Although the API 5C3 and ISO 10400 standards have presented the prediction model of minimum internal pressure yield strength (IPYS) and burst strength for the casing and tubing in the process of strength design, the effect of temperature on the internal pressure strength is not considered completely. It is well known that it is extremely important to understand the failure mechanism of casing and tubing under the synergy of temperature and internal pressure. Hence, the full-scale internal pressure test is performed for N80 casing under temperature and internal pressure by adopting self-developed experimental equipment, by which the important mechanical parameters (such as minimum IPYS, burst strength, stress-hardening rate, and so on) of casing before and after hardening have been obtained. The impacts of temperature on the internal pressure strength are analyzed based on the comparison of test values with theoretical values given by API 5C3 and ISO 10400 standards. Finally, the failure mechanism and hardening characteristic of N80 casing have been clarified under the synergy of temperature and internal pressure. Research results can provide important references for internal pressure strength design of casing in deep well with high temperature.