Abstract
Abstract The development of sandstone-type geothermal energy is an important part of the development of geothermal resources and has great significance in promoting environmental protection and energy structural transformation. In sandstone geothermal energy development, recharging is the main method to ensure bottom hole pressure. However, the pressure and temperature changes of sandstone reservoirs under recharge conditions have not been extensively studied. It is easy to ignore the hydraulic relationship between the production and the injection wells, which leads to an increased risk of thermal breakthrough. Therefore, a three-dimensional hydrothermal coupling model is established, and simulation studies of different flow rates, well lengths, and well spacings are completed in this paper. Here, we show the numerical simulation results. The low temperature expansion zone and hydrostatic pressure near the injection well increase with increasing flow rate, and the maximum expansion of the low temperature zone is about 350 m. The low temperature expansion area near the injection well has a small relationship with the well spacing, and the increase in hydrostatic pressure is proportional to the well spacing. As the length of the well increases, the increase in hydrostatic pressure near the injection well decreases, indicating that the injected water under the long well section easily enters the reservoir. When no thermal breakthrough occurs and the hydrostatic pressure drops significantly near the production well, it is recommended that the flow rate be controlled at approximately 20–25 L/s, the well spacing should be 600–800 m, and the well length should be greater than 100 m.
Highlights
As a major nonrenewable energy source, the fossil energy crisis is one of the biggest challenges facing mankind due to the large-scale consumption of fossil fuels [1]
Salimzadeh et al [13] proposed a strongly coupled THM model that can capture the aperture variation of each fracture induced by the fluid pressure, external stresses, and thermal expansion in the period of production by introducing a strong discontinuity concept into the discrete fracture network (DFN) model
Through the simulation of the model for different flow fluxes, well spacings, and well lengths, the following conclusions are obtained: (1) The pressure change around the injection well is positively correlated with the water injection flow rate
Summary
As a major nonrenewable energy source, the fossil energy crisis is one of the biggest challenges facing mankind due to the large-scale consumption of fossil fuels [1]. Several studies focus on depicting the thermal conduction of a rock mass with discrete fractures, describing heat transfer in the matrix and fractures, which can reveal the actual subsurface heat exchange process during the development period [15, 16]. Pandey et al [18] performed coupled THM simulations using a robust code called Finite Element for Heat and Mass Transfer for a 3-D domain with a single fracture connecting the injection and production wells, studying the evolution of reservoir transmissivity by the influence of hot water extraction and cold water injection. Salimzadeh et al [13] proposed a strongly coupled THM model that can capture the aperture variation of each fracture induced by the fluid pressure, external stresses, and thermal expansion in the period of production by introducing a strong discontinuity concept into the discrete fracture network (DFN) model. A TH coupling model was established to explore the hydrodynamic and temperature fields of the sandstone reservoir under combined irrigation and drainage conditions
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