Numerical Simulation Study on Temperature Transmission in Fracturing Fractures of Deep Shale Oil Reservoirs

Unconventional oil and gas resources play a crucial role in the energy sector and represent a strategic successor in the quest for increased reserves and production. Particularly, the effective development of deep shale reservoirs holds great promise. However, the development of deep shale reservoirs still faces numerous challenges, such as the inevitable temperature field disturbance and thermal effects caused by the injection of low-temperature fracturing fluids into high-temperature shale reservoirs, which significantly impact the rheological properties of the fracturing fluid. Therefore, this paper focuses on the study of temperature transfer in fractures during the injection phase, conducting two-dimensional single-fracture and two-dimensional random fractures THM (Thermo-Hydro-Mechanical) numerical simulation studies. Based on the equilibrium equations of the temperature field, flow field, and stress field, random fractures grid reservoir model was constructed, and finite element numerical simulation studies were carried out using COMSOL. The maximum relative error between analytical and numerical solutions at different locations was 1.11%, thereby verifying the viability of the numerical simulation of the fracture model. A THM coupled numerical simulation study was conducted on the two-dimensional random fractures model, studying the evolution characteristics of the temperature field and flow field, and analyzing the impact of fracture aperture, fracture network density, and formation temperature on random fractures temperature transmission. Changing these three parameters resulted in temperature differences of 47.83 K, 144.35 K, and 100.09 K at a distance of 100 m from the injection well, respectively, and it was analyzed that the fracture network density is the dominant factor affecting the temperature transmission within the random fractures Simultaneously, the rheology of the fracturing fluid was simulated based on the temperature distribution, with the viscosity decreasing from 1.09 mPa·s to 0.06 mPa·s as the temperature of the fracturing fluid changed, exhibiting a decreasing trend.