胶结型深海能源土升温降压联合分解离散元分析

Distinct Element Method Simulation of Bonded type Methane Hydrate Bearing Sediments Exploitation by Thermal Recovery depressurization Combined Method

摘要:

将一个新近提出的考虑温度水压力学综合影响的二维微观胶结模型引入离散元商业软件PFC2D中生成水合物胶结型能源土，通过在双轴试验过程中同时改变温度与反（水）压，在良好排水、排气的条件下模拟了被认为有较好开发前景的升温降压联合开采法，为探索可燃冰开采新方法提供参考.试验结果表明，偏应力小于净砂样破坏偏应力时，开采完成后土体未发生破坏；偏应力大于净砂样破坏偏应力时，开采完成后土体内会产生若干条未充分发展的剪切带；此外，对分解四个不同阶段的微观变量，如接触分布、平均纯转动速率及准静态速度场，进行了较为详细地分析.

关键词:能源土; 升温降压联合分解; 宏微观力学特性

Abstract:

A newly proposed 2D bond model, which took the coupled effects of temperature hydraulic mechanical into consideration, was implemented into the distinct element method (DEM) software Particle Flow Code (PFC2D) to generate methane hydrate bearing sediment (MHBS) that only the bond type methane hydrate (MH) existed. MHBS samples in this simulation were in good drainage and exhaust condition. Then a series of biaxial compression tests were conducted. Results show that when the deviator stress is smaller than the peak deviator stress of pure sand sample, the sample won’t be damaged after dissociation; when the deviator stress is larger than the peak deviator stress of pure sand sample, the MHBS sample will be damaged and several undeveloped shear bands occur. In addition, several micro variables such as contact distribution, averaged pure rotation rate(APR) and quasi static velocity field, were analyzed in four dissociation phases.

Key words:methane hydrate bearing sediments; thermal recovery depressurization combined method; macro and micro mechanical property