天然气水合物降压开采储层稳定性模型分析

储层稳定性是天然气水合物开采所面临的关键问题。本文基于多孔介质流体动力学和弹性力学，建立了天然气水合物降压开采储层稳定性数学模型，包括储层沉降和井壁稳定性分析两个方面，并以墨西哥湾某处水合物藏的基本参数为例，进行了水合物降压开采储层稳定性的模拟计算。结果表明，在水合物降压开采的过程中，孔隙流体压力降低导致了储层的沉降，最大的沉降发生在井壁附近，水合物分解会加剧储层的沉降；降低井孔压力会造成井壁破坏的潜在危险，在井壁附近，周向和垂向应力达到最大处容易发生失稳破坏，地层的水平应力差会增加井壁的不稳定性。

A Geomechanical Stability Model Analysis of Hydrate Reservoir for Gas Hydrate Production by Depressurization

A model based on the dynamics of fluids in porous media and poroelasticity is developed for analyzing geomechanical stability of hydrate reservoir, which is a challenge for commercial gas production from hydrate reservoir. This model, including subsidence of hydrate reservoir and wellbore stability, is applied to Gulf of Mexico, where the basic parameters and the in situ stresses are publicly published. It is concluded that subsidence of hydrate reservoir occurs due to the changes in pore pressure and the maximum subsidence occurs near the wellbore; the more hydrates decompose, the larger subsidence occurs. Decreasing well pressure will induce potential wellbore failure and the borehole failure is expected to initiate at those positions where the tangential and vertical stresses reach the maximum value. The horizontal stress contrast increases the instability of wellbore.