An Efficient Hydromechanical Coupling Simulation of Fracturing-Flooding Enhanced Oil Recovery Process Based on Damage Mechanics and Its Application for Shengli Shale Oil Reservoirs

Summary Fracturing-flooding combines hydraulic fracturing equipment with waterflooding development, which can replenish formation energy in a short time by high-pressure and high-rate water injection. Due to the injection pressure being higher than the breakdown pressure of the formation, it induces extensive microfractures within the formation, which significantly improves the reservoir’s properties and consequently enhances oil production. The typical block of Shengli shale oil has a high production rate in the early stage of development, but the production declines rapidly in the later stage, and then increases significantly after fracturing-flooding. However, the theoretical understanding of fracturing-flooding remains insufficient, and there is a lack of corresponding numerical simulation methods for fracturing-flooding hydromechanical coupling. Aiming at this problem, we conducted numerical simulation research on Shengli shale oil fracturing-flooding for this paper: Based on the oil/water continuity equation, Biot poroelastic constitutive model, and continuum damage mechanics model, a hydromechanical coupling mathematical model of fracturing-flooding is established, and the damage factor calculation method of Shengli shale is obtained based on the discrete element method (DEM) analysis. This model is solved using the finite volume method and finite element method to address the porous flow and stress equations, respectively. Combined with the two-grid system, the numerical solution of hydromechanical coupling for corner-point grid is realized, and a hydromechanical coupling numerical simulation method for the Shengli shale oil fracturing-flooding process is formed. Furthermore, we analyze the impact of rock heterogeneity, injection rate, in-situ stress, injection period, and other factors on fracturing-flooding efficiency, and match it with the production data of the typical mine block. The results verify the correctness of the method proposed in this paper. On the basis of the history matching, the development plan of the Shengli shale oil typical block for the next 10 years has been carried out.