On a Method of Prediction of the Annular Pressure Buildup in Deepwater Wells for Oil & Gas

摘要

In deepwater wells for exploration and exploitation of oil & gas, the wellhead structure is of importance, and the annular pressure cannot be released after the casing hanger is set. The pressure changes in the casing annuli, caused by the temperature changes during the drilling and production processes, will increase the risk of failure of the casing. Therefore, a study of the safety of the casing in deepwater wells, by considering the complex engineering factors, will be of both academic as well as practical significance. In this paper, a model for the interactions among the casing-cement-formation system is established, by considering the thermal loading in a perfect well section. The deformation of the casing, as related to the temperature and the internal pressure of the casing, is obtained through a theoretical derivation. The theoretical model, established in the present paper, can be used to predict the annular pressure buildup caused by the thermal expansion of both the casing and the annular fluid. The present research shows that the annular pressure caused by a temperature change can lead to the failure of the casing, when the average temperature change is high enough. Therefore, the effects of temperature and pressure should be taken into account specially in the casing design for deepwater wells for oil & gas.