To extract geothermal energy from low-permeability reservoirs: Development and simulation of cyclic water injection (CWI)- and water-assisted gravity drainage (WAGD)-based processes

Type:

Research Report, Student Research

Link:

To extract geothermal energy from low-permeability reservoirs: Development and simulation of cyclic water injection (CWI)- and water-assisted gravity drainage (WAGD)-based processes

Authors:

Runzhi Li, Jianfei Chen, Yee-Chung Jin, Jinkai Xue, Na Jia

Citation:

Li, R., Chen, J., Jin, Y.-C., Xue, J., & Jia, N. (2022). To extract geothermal energy from low-permeability reservoirs: Development and simulation of cyclic water injection (CWI)- and water-assisted gravity drainage (WAGD)-based processes. Results in Engineering, 15, 100563.

Abstract:

Geothermal energy is a clean energy source to fulfill the increasing global energy demands. For the first time, several energy extraction strategies are proposed and compared through numerical simulations for effective energy recovery from low-permeability geothermal reservoirs. We simulate geothermal energy extraction using either Cyclic Water Injection (CWI) or Water-Assisted Gravity Drainage (WAGD) processes with or without hydraulic fracturing over a 10-year operation. We evaluate the positioning of injector and producer in WAGD process, well spacing, addition of one injector, and the time variation of injection/soaking periods in CWI process. The simulations indicate that the fractured reservoirs generate more energy than those without fracturing; CWI-based processes exhibit higher energy recovery efficiency than WAGD process in terms of Energy-Water-Ratio (EWR). EWR, as a newly proposed parameter in this study, is defined as the energy production specific to per unit volume of water injected, which is useful in evaluating the cost-effectiveness of a geothermal energy extraction process. The gravitational effect proves to be the dominant factor that determines energy generation compared to phase change in WAGD process. In addition, formation and impacts of steam chambers in CWI and WAGD-based processes are discussed. Furthermore, statistical analyses are performed to evaluate the effects of reservoir temperature, pressure, permeability, and their mutual interactions on cumulative energy production. Eventually, two correlation models for predicting cumulative energy production based on these formation properties are proposed. This study provides a new perspective on implementing different innovative exploration strategies and optimization processes for energy extraction from low-permeability geothermal reservoirs.

Acknowledgments:

The authors would like to appreciate the support from the Petroleum Systems Engineering and Environmental Systems Engineering programs at the Faculty of Engineering and Applied Science of the University of Regina. This study was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) through the NSERC Discovery Grants (N. Jia and J. Xue) and Discovery Launch Supplement Grant (J. Xue). The authors would like to acknowledge the financial support from the Petroleum Technology Research Centre (PTRC) and Mitacs Canada to N. Jia. J. Chen would like to thank the Saskatchewan Innovation and Excellence Graduate Scholarship. J. Xue is grateful for the Results in Engineering Young Investigator Award 2022.

Keywords:

Energy-Water-Ratio (EWR), Hydraulic fracturing (HF), Geothermal reservoir simulation, Enhanced geothermal system (EGS), Steam chamber, Well spacing, Well configuration, Cumulative energy production, Sensitivity analysis, Box, Behnken experimental design