Simulation of Water Influx and Gasified Gas Transport during Underground Coal Gasification with Controlled Retracting Injection Point Technology

Yanpeng Chen, Tianduoyi Wang, Jinhua Zhang, Mengyuan Zhang, Junjie Xue, Juntai Shi, Yongshang Kang and Shengjie Li
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Yanpeng Chen: Petroleum Exploration and Development Research Institute, PetroChina, Beijing 100083, China
Tianduoyi Wang: Coalbed Methane Research Center, China University of Petroleum (Beijing), Beijing 102249, China
Jinhua Zhang: Petroleum Exploration and Development Research Institute, PetroChina, Beijing 100083, China
Mengyuan Zhang: Petroleum Exploration and Development Research Institute, PetroChina, Beijing 100083, China
Junjie Xue: Petroleum Exploration and Development Research Institute, PetroChina, Beijing 100083, China
Juntai Shi: Coalbed Methane Research Center, China University of Petroleum (Beijing), Beijing 102249, China
Yongshang Kang: College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China
Shengjie Li: College of Geophysics and Information, China University of Petroleum (Beijing), Beijing 102249, China

Energies, 2022, vol. 15, issue 11, 1-29

Abstract: Underground coal gasification (UCG) may change the energy consumption structure from coal-dominated to gas-dominated in the years to come. Before that, three important problems need to be solved, including failure of gasification due to large amounts of water pouring into the gasifier, environmental pollution caused by gas migration to the surface, and low calorific value caused by poor control of the degree of gasification. In this study, a geological model is first established using the computer modeling group (CMG), a commercial software package for reservoir simulation. Then, the inflow of coal seam water into the gasifier during the controlled retracting injection point (CRIP) gasification process is simulated based on the geological model, and the maximum instantaneous water inflow is simulated too. Meanwhile, the migration of gasified gas is also simulated, and the migration discipline of different gases is shown. Finally, the pressure distributions in two stages are presented, pointing out the dynamic pressure characteristics during the UCG process. The results show that (a) the cavity width, production pressure, and gasifier pressure are negatively correlated with the maximum instantaneous water inflow, while the initial formation pressure, injection pressure, coal seam floor aquifer energy, and temperature are positively correlated; (b) CO 2 is mainly concentrated near the production well and largely does not migrate upward, O 2 migrates upward slowly, while CH 4 , CO and H 2 migrate relatively quickly. When the injection–production pressure difference is 2 MPa, it takes 33.5 years, 40 years, and 44.6 years for CH 4 , CO, and H 2 to migrate from a depth of 1000 m to 200 m, respectively. When the pressure difference increases to 4 MPa, the gas migration rate increases about two-fold. The aquifer (3 MPa) above a coal outcrop can slow down the upward migration rate of gas by 0.03 m/day; (c) the pressure near the production well changes more significantly than the pressure near the injection well. The overall gasifier pressure rises with gasifier width increases, and the pressure distribution always presents an asymmetric unimodal distribution during the receding process of the gas injection point. The simulation work can provide a theoretical basis for the operation parameters design and monitoring of the well deployment, ensuring the safety and reliability of on-site gasification.

Keywords: underground coal gasification (UCG); controlled retraction injection point (CRIP); water inflow; gas migration; pressure distribution (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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