基于连续-离散介质耦合的水合物储层出砂数值模拟

出砂是制约天然气水合物安全高效长期可控开采的瓶颈之一，出砂现象的诱因及其演化规律与水合物储层动态响应行为密切相关。据此，提出了一套研究水合物开采过程中储层动态响应与出砂行为的综合数值模拟方法，并以大尺寸开采出砂防砂模拟反应釜为研究对象，以水合物胶结模式为例，分析了实验尺度下模拟水合物储层在不同开采压差条件下的储层物性、力学响应和流固体（水、气和砂）运移产出规律。结果表明：实验尺度降压开采过程中，体系温度存在快速降温、持续低温和温度回升3个阶段；水合物分解引起的气水产出和井周应力集中是水合物储层出砂的关键控制因素；同一开采压差条件下，提高水流速会导致地层出砂量增加，并且出砂速率的增幅随水流速的增大而增大，而缩小防砂筛孔孔径能够延缓出砂起始时间，并且使得出砂量显著减少。

Continuum-discrete coupling method for numerical simulation of sand production from hydrate reservoirs: a lab-scale case study

Sand production is one of the bottlenecks restricting the safe, efficient and long-term controlling gas production from natural gas hydrate-bearing sediments (GHBS). The inducement and evolution law of sand production are closely related to the dynamic response behavior of GHBS. On this basis, this paper proposes a comprehensive numerical simulation method for studying the dynamic response of reservoirs and sand production behavior during gas production from GHBS. Further, taking the large-size sand production and sand control simulation device as the research object, and the cementation mode of hydrate as a case, this paper analyzes the physical property and mechanical responses, migration and production laws of fluids and solids (water, gas, and sand)of the simulated hydrate reservoirs under different production pressure drops at the laboratory scale. The results show that during depressurization development of the laboratory scale, the system temperature has experienced three stages:rapid cooling, sustained low temperature, and temperature rise; gas-water production and stress concentration around the well caused by hydrate decomposition are the key control factors for sand production in hydrate reservoirs; under the same production differential pressure, increasing the water velocity will increase the sand production, and the sand production rate will increase with the increasing of water velocity. The reduction of the sand control sieve aperture can delay the starting time of sand production, and significantly decreases sand production.