Numerical simulation of multi-fracture propagation in staged multi-cluster SC-CO2 fracturing of horizontal wells

Abstract

Numerical simulation research on fracture propagation in SC-CO2 (supercritical carbon dioxide) fracturing mainly focuses on a single fracture, and the multifracture propagation law of SC-CO2 fracturing under the influence of multiple factors is ambiguous. In this study, based on the boundary element method, a three-dimensional, plane propagation model of multicluster SC-CO2 fracturing in multifractured horizontal wells, which considers the three-dimensional, elastic deformation of the reservoir rock mass, the two-dimensional flow of SC-CO2 fracturing fluid in fractures, the change in SC-CO2 physical parameters during fracturing and the flow distribution of each cluster fracture, is established. The influence of geological factors and construction factors on the propagation law of SC-CO2 fracturing in multifractured horizontal wells is explored. The results show that compared with slick water fracturing, the hole friction of SC-CO2 fracturing effectively balances the negative effect of induced stress between two fractures, inhibits the liquid entry advantage of heel-end fractures, and increases the reconstruction area in the reservoir. SC-CO2 fracturing in multifractured horizontal wells minimizes the energy loss of the fracture tip in different ways with different reservoir stress differences. Increasing the displacement and crack spacing are conducive to promoting the uniform expansion of SC-CO2 multicrack propagation. Based on the liquid volume distribution index, the construction parameters are optimized. The construction displacement of SC-CO2 multicluster fracturing should be greater than 10 m3 min−1, the hole diameter should be less than 14 mm, and the number of boreholes in each perforation cluster should be less than 16.