Hydrothermal behaviors of geomaterials with multiple fracture channels: Effect of intersecting “X” and “Y” shape fractures

Abstract

The water flow and heat transfer characteristics within fractured geomaterials have significant practical applications in various fields, including deep geothermal resource development and oil and gas extraction. However, the presence of numerous intersecting fracture networks in geothermal systems complicates the hydrothermal coupling process in fractured geomaterials. Therefore, in this study, a multiphase microcontinuum approach is introduced to systematically study the hydrothermal coupling behavior in a multichannel fractured rock mass. Initially, a numerical model for water flow and heat transfer in fractured rock masses was established, and the accuracy and reliability of the multiphase microcontinuum method were verified through experiments. Two representative intersecting fractures in the rock mass, namely, “X”-shaped and “Y”-shaped fractures, were subsequently considered to delve into the effects of key parameters, such as the fracture aperture, water injection velocity, intersection angle of fractures, and water injection strategy, on the heat transfer performance of the fractured rock mass. Additionally, rock with parallel fracture channels was established to compare and investigate the heat transfer effect between water and rock masses with different fracture channel shapes. The results indicate that the fracture aperture, water flow rate, and intersection angle of fractures have substantial control over the heat transfer effect in fractured rock masses, whereas adjustments to the water injection method have a limited overall impact on the final heat transfer effect. Compared with single fracture channels, multichannel fractures can effectively enhance the heat transfer effect, and the shape and distribution of fracture channels significantly influence the heat exchange efficiency of fractured rock masses.