Numerical Simulation and Optimization of Well Parameters for Depressurization-Assisted CO2 Replacement Using a PSO Algorithm

• Published in: Energy & fuels Vol. 38; no. 11; pp. 9722 - 9733
• Main Authors: Guo, Yang, Li, Shuxia, Huang, Xin, Song, Zhongxue, Liu, Junhao, Sun, Hao, Liu, Lu, Zhang, Ningtao
• Format: Journal Article
• Language: English
• Published: American Chemical Society 06.06.2024
• Subjects: algorithms; carbon dioxide; dissociation; energy; gas hydrate; mathematical models; temperature; Unconventional Energy Resources
• ISSN: 0887-0624; 1520-5029; 1520-5029
• DOI: 10.1021/acs.energyfuels.4c01313

Natural gas hydrate (NGH) is a solid clathrate compound formed by water and natural gas at low temperatures and high pressures characterized by abundant resources and a wide distribution. The depressurization-assisted CO2 replacement method has the advantage of concurrently producing CH4 while sequestering CO2, rendering a promising approach for exploiting NGH. Some experiments have been conducted on depressurization-assisted CO2 replacement. However, a comparative analysis of the depressurization and CO2 replacement application sequences remains ambiguous. In this study, a numerical model for depressurization-assisted CO2 replacement was established to clarify the application sequences, analyze the influence of different factors, and propose the optimal production scheme based on the optimization algorithm. Results indicated that the formation of the CO2 hydrate promoted the dissociation of the CH4 hydrate. Depressurization, followed by CO2 replacement represented the optimal production sequence, with cumulative gas production (V p) and CO2 sequestration ratios (R CO2) higher than those of CO2 replacement, followed by depressurization by 3.17 and 1.61%, respectively. As the production pressure decreased from 7 to 3 MPa, both V p and R CO2 increased. The CO2 injection rate had little effect on V p but affected R CO2, while the CO2 injection temperature had less effect on any of them. According to the particle swarm optimization algorithm (PSO) results, the optimal scheme was a bottom hole pressure of 3 MPa, a CO2 injection rate of 7000 m3/d, a CO2 injection temperature of 22 °C, and a production and injection well spacing of 280 m. This study provides insights into the potential applications of depressurization-assisted CO2 replacement in the field tests of hydrate production.