水力压裂技术诱导冻融水合物储层增产数值模拟

A Numerical Study on Freeze-thaw Hydrate Reservoir Exploitation Induced by Fracturing Technology

郝国强 侯嘉欣 段硕 李新旺 申鹏飞

HAOGuoqiang HOUJiaxin DUANShuo LIXinwang SHENPengfei

广东省可再生能源重点实验室, 广东 广州 510640 河北工程大学矿业与测绘工程学院, 河北 邯郸 056038 自然资源部天然气水合物重点实验室·青岛海洋地质研究所, 山东 青岛 266237

Guangdong Provincial Key Laboratory of Renewable Energy, Guangzhou, Guangdong 510640, China School of Mining and Geomatics Engineering, Hebei University of Engineering, Handan, Hebei 056038, China Key Laboratory of Gas Hydrate, Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao, Shandong 266237, China

冻土区天然气水合物开采过程中冰相生成增加了天然气在储层内的运移难度，因此，增加天然气产量和减少冰的产生对储层内气体运移阻塞影响是冻融水合物储层高效开发面临的关键问题。以祁连山冻土区DK-2站位储层参数为基础，提出降压与水力压裂协同开发策略。通过数值模拟系统评估压裂带半径（0~5 m）和渗透率（1~1 000 mD）对开采效果的影响。研究表明，水力压裂形成的改性储层区可有效抑制冰相堵塞，加速压力传递与气体运移。当压裂带半径由0增至5.0 m时，天然气30 a的累计产量提升219%，其中前10 a贡献率达54.8%，储层总体分解率为48.7%。参数敏感性分析表明，压裂带渗透率超过100 mD后增产效果趋缓，最优压裂半径取4 m。该研究成果为冻土区水合物开采中冰堵效应的工程调控提供了理论依据，揭示了储层改造对提升气水两相运移效率的重要作用。

The formation of ice phase during the exploitation of natural gas hydrates in permafrost regions increases the difficulty of gas migration within the reservoir. Therefore, enhancing gas production and reducing ice formation to alleviate the blockage of gas migration in the reservoir are key issues for the efficient development of frozen-thawed hydrate reservoirs. Based on the reservoir parameters of the Well DK-2 in the Qilian Mountain permafrost region, this paper proposes a combined development strategy of depressurization and hydraulic fracturing. Through numerical simulation, the influence of the fracture radius (0~5 m) and permeability (1~1 000 mD) on the exploitation effect is systematically evaluated. The research shows that the modified reservoir area formed by hydraulic fracturing can effectively inhibit ice phase blockage and accelerate pressure transmission and gas migration. When the fracture radius increases from 0 m to 5 m, the cumulative gas production over 30 years increases by 219%, with a contribution rate of 54.8% in the first 10 years, and the overall reservoir decomposition rate is 48.7%. The parameter sensitivity analysis indicates that the production enhancement effect slows down when the fracture permeability exceeds 100 mD, and the optimal fracture radius is recommended to be 4 m. This research provides a theoretical basis for the engineering control of ice plugging effects in permafrost hydrate exploitation and reveals the significant role of reservoir modification in improving the efficiency of two-phase gas and water migration.

10.11885/j.issn.1674-5086.2022.11.25.01