| Title | A New Numerical Model of Thermal Aperture Changes in an Enhanced Geothermal System Reservoir |
|---|---|
| Authors | M.D. Aliyu, R.A. Archer |
| Year | 2020 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Thermal aperture, hydro-mechanical aperture, combined aperture, EGS reservoir, THM simulation |
| Abstract | Extraction of energy from deep crystalline formation requires pressurisation of the rock mass to create new or enhance existing natural fractures. The fractures generate a pathway for transport of the fluid and heat back to the surface for optimum energy production. However, the complexity of fracture aperture opening and closure during exploitation has posed a challenge for both engineers and geologists. The most widely used model for fracture aperture changes is frequently limited to the hydro-mechanical effect only. This paper presents a new model that incorporates a complete cycle of thermal, hydraulic and mechanical aperture changes in an enhanced geothermal system (EGS) reservoir using a coupled thermo-hydro-mechanical (THM) simulator. The goal is to understand the extent to which thermal aperture changes might enhance the performance of EGS reservoirs. Three reservoir cases are developed: a model of hydro-mechanical aperture changes with a constant thermal aperture; a model of thermal aperture changes employing a constant hydro-mechanical aperture; and a combined model of both hydro-mechanical and thermal aperture changes. The outcomes show that the changes are greater with the thermal aperture than with the hydro-mechanical aperture due to the impact of thermal contraction. |