Numerical Investigation of CO<sub>2</sub> Storage Capacity via Hydrate in Deep-Sea Sediments
Zhi Liu, Jianchun Xu, Hangyu Li, Shuxia Li, Xingwen Fan
Abstract
Reducing CO 2 emissions has drawn more attention because of concerns about climate change. With the exploitation of natural gas hydrate reservoirs, depleted hydrate reservoirs may provide an ideal space for the long-term storage of CO 2 . However, the feasibility and amount of CO 2 storage in hydrate reservoirs must be studied. The process of CO 2 reacting with water to form hydrate is always analyzed based on the numerical simulation software CMG-STARS. The CO 2 hydrate phase equilibrium curves can be fitted by a variety of methods, including PVTSim, PipeSim, CSMGem, and HP-μDSC. In this paper, we focus on the high-pressure part of the phase equilibrium curves for pressure greater than 4500 kPa, which are accurately fitted. Estimates of CO 2 storage can vary by 1.91 times between different phase equilibria due to the resulting hydrate plugging. Numerical simulation models are established to predict the CO 2 storage capacity via hydrates in deep-sea sediments. A series of sensitivity parameter analyses are conducted to study the CO 2 hydrate distribution and storage volume. The main parameters include permeability, rock compressibility factor, injection temperature, maximum bottomhole pressure, and injection rate. By increasing the reservoir pore volume and decreasing the hydrate plugging, the storage volume can effectively increase. Moreover, when hydrate plugging occurs around the wellbore, hydraulic fracturing can create a highly conductive path, resulting in an increase in storage volume from 2.20 × 10 7 to 3.60 × 10 7 m 3 .