| Title | Numerical Investigation of the Effects of Caprock on Subsurface Temperature and Heat Flow Distributions |
|---|---|
| Authors | Hui Wu, Weiwei Ma, Bo Zhang, Jinjiang Zhang |
| Year | 2023 |
| Conference | World Geothermal Congress |
| Keywords | Geothermal reservoir, caprock, heat flow, temperature distribution, thermal conductivity |
| Abstract | The efficient exploitation of geothermal reservoirs relies on the understanding of subsurface temperature distribution, which highly depends on the geological conditions of the crust in which the reservoirs reside. A caprock with a relatively low thermal conductivity is essential to the formation of high-temperature geothermal reservoirs. To understand the effects of caprock on subsurface temperature distribution and heat flow profile, we developed a 2D model to simulate the evolution of temperature distribution under continuous heat input from the model bottom. The model involves a sediment layer with a relatively low thermal conductivity on top of a thick granite layer. Radiogenic heat generation is also considered in the granite layer. Both temperature and vertical heat flow are significantly altered by the caprock. The presence of the caprock leads to the increase of the underlying rock temperature and meanwhile the decrease of surface heat flow. Compared with locations without a caprock, a location covered by a caprock exhibits smaller surface heat flow but higher underlying rock temperature. The thicker the caprock layer and the lower the caprock thermal conductivity, the more significant the impacts that the caprock exerts on the temperature and heat flow distributions. Radiogenic heat generation increases both rock temperature and vertical heat flow. The combination of caprock and radiogenic heat generation together leads to a first increasing and then decreasing pattern in the profile of vertical heat flow from the bottom of the radiogenic heat generation domain to the model surface. Results from the current study indicate that the interpretation of field heat flow/temperature measurements and the identification of high temperature geothermal reservoirs should consider realistic geological conditions, especially the existence of caprock layers and the corresponding thermal properties of the caprocks. |