AUTHOR=Zhang Bo , Zheng Yushan , Deng Jinrui , Lu Nu , Cao Lihu , Wang Qing , Luo Lihong 

TITLE=Modeling analysis of the temperature profile and trapped annular pressure induced by thermal-expanded liquid in a deep gas well

JOURNAL=Frontiers in Physics

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2022.1014842

DOI=10.3389/fphy.2022.1014842

ISSN=2296-424X

ABSTRACT=The trapped annular pressure(TAP) caused by the thermal expansionis one of the serious challenges for the safe production of the deep gas well. Therefore, this paper proposes a model to calculate the temperature profile of the deep gas well based on the heat transfer process and the gas properties. With the help of the temperature model, the TAP in the tubing-casing annulus is analyzed according to the annular fluid distribution and the volume consistence law. The results indicate the temperature inside tubing string decreases faster under higher bottom hole pressure. When the tubing-casing annulus is totally filled with the annular protection liquid, the TAP continues increasing with the production rate. Considering the high production rate, the TAP is inevitable and high enough to damage the integrity of the deep gas well. The nitrogen gas mitigates the TAP by reducing the annular liquid volume and providing the extra space to accommodate the thermal-expanded annular liquid. The good mitigation performance can be achieved no matter how large the production rate is. The mitigation performance can be divided into the fast decreasing stage, the efficient control stage and the stable stage three stages as the nitrogen gas column length increases. The compression of the nitrogen gas volume plays a major role in the fast decrease stage while the reduce of the annular liquid plays a major role in the stable stage. For the best cost-effective, the nitrogen gas column is recommend in the efficient control stage and should not exceed 15%.