Propagation patterns of hydraulic fractures in deep tight sandstone reservoirs based on thermo-fluid-solid-chemical coupling

The deep tight sandstone gas reservoirs in the northern slope belt of the Kuqa Depression, Tarim Basin, are key area for natural gas reserve expansion and production enhancement in China, and hydraulic fracturing technology for these reservoirs is a critical means for hydrocarbon production enhancement. However, the complex geological conditions in deep layers lead to unclear propagation patterns and influencing factors of hydraulic fractures, requiring quantitative analysis to reveal the propagation patterns of hydraulic fractures under the action of multi-field coupling. Focusing on the high-temperature and high-pressure geological environment of deep gas reservoirs in the northern slope belt of the Kuqa Depression, a thermo-fluid-solid-chemical coupling model was established considering geomechanical factors such as "stress and fracture weak planes". Using finite element numerical simulation, the propagation patterns of hydraulic fractures were elucidated. The results showed that: (1) The dynamic propagation process of hydraulic fractures was significantly influenced by thermo-fluid-solid-chemical coupling, which determined the propagation patterns of hydraulic fractures. (2) Complex fracture networks tended to form in zones with low horizontal stress differences, and differences in horizontal stress gradient induced asymmetric propagation of hydraulic fractures. (3) During the propagation of hydraulic fractures, natural fractures were preferentially activated, and the occurrence of natural fractures affected the propagation direction of hydraulic fractures. When the angle between natural fracture and hydraulic fracture was large, the propagation of hydraulic fractures tended to stop and pass through natural fractures. When the angle was small, hydraulic fractures tended to activate natural fractures or both activate and pass through them. (4)The perforation inclination angle was positively correlated with the fracture deflection angle. The effect of injection rate on fracture area had an optimal upper limit. A greater temperature difference between fracturing fluid and formation more easily generated tensile fractures and resulted in a lower fracture initiation pressure.