MODELING STUDY ON THE S-CO₂ FRACTURING OF RESERVOIRS WITH DIFFERENT ROCK MATRIX PERMEABILITY

In recent years, supercritical carbon dioxide(S-CO₂)has been considered as a promising fracturing fluid, which shows higher fracturing capacity compared with water-based fracturing fluid. However, an obvious defect of intensifying leak off occurs when S-CO₂ is used for HF in reservoir rocks with relatively high matrix permeability. In this paper, simulations of the applicability of water fracturing(WF) and S-CO₂ fracturing(SCF)in reservoirs with different RMP were conducted. Compared with water-based fracturing fluid, S-CO₂ has lower viscosity and density under the same conditions, which makes it easier to form more complex fracture networks. However, especially in reservoirs with relatively higher RMP, the intensifying leak off of S-CO₂ from the fracture propagation can seriously affect the establishment of fracture fluid pressure and the propagating of fractures. In this case, increasing the injection rate of fracturing fluid can shorten the fracturing time, so as to effectively reduce the impact of leak off. Modeling results clearly demonstrate the importance of rock matrix permeability, which can be directly used for the theoretical guidance of S-CO₂ fracturing applicability and production capacity.