A Comparative Study of Hydrate-Based CO<sub>2</sub> Sequestration at Different Scales
Weixin Pang, Mingqiang Chen, Qiang Fu, Yang Ge, Xiaohan Zhang, Huiyun Wen, Shouwei Zhou, Qingping Li
Abstract
As a novel pattern of CO 2 geological sequestration, hydrate-based CO 2 storage has attracted significant attention due to relatively mild sequestration environments, a rapid hydration rate, widely distributed storage sites, and good stability. Figuring out the regularity of CO 2 dynamic injection, migration and hydration in porous media is crucial for achieving efficient hydrate-based CO 2 sequestration in marine sediments. In this work, the impacts of CO 2 injection well types and sequestration layers on hydrate formation and conversion rates were first investigated using a small-scale experimental apparatus. The plugging phenomenon at different positions, including the wellhead, nearby formation, and displacement channels caused by CO 2 hydrate generation, was revealed. Subsequently, comparative magnification experiments of hydrate-based CO 2 sequestration were conducted based on the self-developed large-scale platform, where a similar phenomenon was discovered. Results show that there are significant differences in the increased temperature magnitude at each layer, indicating a small CO 2 propagation and hydrate formation range with vertical CO 2 injection wells. The CO 2 sweep range and hydrate formation area are larger when horizontal wells are employed for CO 2 injection. The use of multilaterally perforated horizontal wells for CO 2 injection yields the highest hydrate-based CO 2 sequestration efficiency. Meanwhile, injecting CO 2 from the underlying layers, after preferentially forming an artificial CO 2 hydrate cap in the overlying layers, is more conducive to the formation of large amounts of hydrate. CO 2 injection through multiple layers results in a higher hydrate conversion rate compared to single-layer injection. The findings in this work are of great significance for understanding the mechanism of CO 2 hydrate formation at different scales and provide data support for field-scale hydrate-based CO 2 sequestration in the future.