Numerical simulation of multi-fracture uniform propagation in naturally fractured reservoirs based on the continuum–discontinuum method

Abstract

Multi-cluster fracturing technology with horizontal wells is significant for the production enhancement of unconventional reservoirs. However, affected by the natural fracture distribution in the reservoir, stress shadowing between multi-fractures and perforation erosion has non-negligible influence on the multi-fracture uniform propagation, which results in uneven reservoir stimulation and lower production capacity. In this study, a multi-field coupled stress-seepage-fracture model for hydraulic fracturing of fractured reservoirs based on the continuum–discontinuum method was developed, adequately simulating the full scenario of stress disturbances, perforation erosion, and fracture interactions during the fracturing process. The effect of different geological and engineering parameters on the competing propagation of multi-fractures was investigated in detail, and the results show: Different geological and engineering parameters have significant influence on the competitive propagation of multi-fractures; among the geological parameters, the elastic modulus has the highest impact on the uniform fluid intake of multi-fractures, while the horizontal stress difference has the least impact on the uniform fluid intake of multi-fractures. Among the engineering parameters, the effect of natural fracture angle on the standard deviation of the fluid injection volume is gradually reduced with the increase in perforation number, flow rate, and fluid viscosity. For a low number of perforations and high fluid viscosity, both have great influence on promoting uniform fluid entry in multiple fractures. In addition, geological parameters have a significantly greater influence on the merging of multi-fractures than engineering parameters, and the probability of merging of multi-fractures increases significantly under low stress differentials and long natural fractures.