井液侵入水合物储层井壁力学稳定性分析

Wellbore Stability Analysis of Drilling Fluid Invading Hydrate Reservoir

王磊

WANGLei

中国石化石油工程技术研究院, 北京 朝阳 100101 中国石油大学(北京)石油工程学院, 北京 昌平 102249

Research Institute of Petroleum Engineering, SINOPEC, Chaoyang, Beijing 100101, China College of Petroleum Engineering, China University of Petroleum, Changping, Beijing 102249, China

海洋天然气水合物储层钻井过程中，钻井液易侵入天然气水合物井壁，引起井壁坍塌失稳。天然气水合物地层的坍塌压力与低温下的水合物相平衡压力的耦合作用是引起井壁失稳的重要因素。因此，开展低温钻井液体系作用下水合物储层井壁稳定性评价实验，研究钻井液侵入造成天然气水合物井壁失稳的机理，对于海洋天然气水合物顺利开采具有极大意义。通过模拟海洋环境下的温度、压力，制备水合物岩芯，并注入不同体系的钻井液，监测天然气水合物岩芯内的温度、压力、力学特征参数及水合物质量丰度的变化，从水合物岩芯物性变化出发研究钻井液体系对井壁稳定性的影响。研究表明，温度较高的钻井液体系，在侵入后会使近井壁峰值强度大幅降低，更易引起井壁坍塌；较大的水合物质量丰度也会引起水合物岩芯参数的波动变化。与未入侵岩芯相比，当钻井液入侵5 min后，岩芯应力峰值点平均下降了13.95%，更易发生井壁失稳。

During the drilling of marine gas hydrate reservoirs, the drilling fluid easily invades the gas hydrate wellbore, causing the collapse and instability of the wellbore. The coupling effect of the collapse pressure of the gas hydrate formation and the hydrate phase equilibrium pressure at low temperature is an important influencing factor. Therefore, it is of great significance for the smooth exploitation of marine gas hydrate to carry out the evaluation experiment of the wellbore stability of hydrate reservoir under the action of low temperature drilling fluid system, and to study the mechanism of gas hydrate wellbore instability caused by drilling fluid invasion. The hydrate cores are prepared by simulating the temperature and pressure at the depth of the ocean, and by injecting drilling fluids of different systems, the temperature, pressure, mechanical characteristic parameters and hydrate mass abundance changes in the gas hydrate cores are monitored, and different conditions are studied. Wellbore stability under influence. The research shows that as the drilling fluid temperature increase, the peak strength near the wellbore after the invasion decrease. Large hydrate mass abundance also causes the fluctuation of hydrate core parameters. Compared with the uninvaded core, the stress peak point of the core decrease by 13.95% on average after 5 min of intrusion.

10.11885/j.issn.1674-5086.2022.03.29.03