Study of CO2 injection to enhance gas hydrate production in multilateral wells

Multilateral wells offer promising opportunities for the commercial development of natural gas hydrates. The reservoir strength and stiffness weaken as hydrates decompose during the depressurization production process, potentially leading to formation subsidence, seabed inclination, and other associated geomechanical risks. Thus, understanding the geomechanical issues surrounding the wellbore is crucial for attaining safe and efficient hydrate development. This paper develops a three-dimensional numerical model to simulate the production capacity of hydrate reservoirs through CO2 injection in multilateral wells. The study compares the pressure and temperature response of the reservoir, the characteristics of gas and water production, the variation in hydrate and methane saturation, the productivity, and the geological subsidence patterns during the extraction process. Results indicate that hydrates generated through CO2 injection inhibit methane hydrate decomposition, with delayed injections resulting in higher cumulative yields. CO2 injection can restore reservoir pressure and mitigate formation subsidence. The combined depressurization method, which involves CO2 injection in multilateral wells, can increase hydrate production while preserving formation stability, offering a potential approach for commercial hydrate exploitation. This approach is anticipated to advance the industrialization of gas hydrate extraction and propose a new possibility for CO2 utilization to curb climate change.