Study on Fracture Propagation Simulation with the Integration of Fully-Coupled Geomechanical and DFN Modeling

Abstract

Shale gas reservoirs are characterized in low gas abundance, poor permeability, lower natural productivity than the lower limit of industrial oil flow, and rapid formation energy decline. At present, the technology of horizontal well drilling and staged hydraulic fracturing is widely used for the exploitation of such low-porosity and low-permeability reservoirs. The long well section of the horizontal well in the reservoir and the hydraulic fractures formed by fracturing act as the "underground expressway" for the deep gas in the reservoir to flow toward the wellbore. Their combination can greatly increase the production performance of the oil and gas resources in the reservoir. Staged multi-cluster fracturing in horizontal wells is the key technology to achieve the profitable shale gas production. The results of on-site downhole perforation imaging and distributed optical fiber temperature and acoustic monitoring show that there are obvious non-uniform liquid inflow and expansion phenomena in each cluster of fractures during the fracturing process. Relevant research results also show that factors such as the heterogeneity of the reservoir and the stress interference caused by the propagation of multiple fractures are the main causes of the non-uniform propagation of hydraulic fractures. Therefore, it is accessible to simulate the complex balanced expansion of each cluster of fractures in the fracturing section to improve the coverage of hydraulic fractures in the horizontal well section with numerical simulation methods based on the basic theory of elasticity and fracture mechanics, to reveal how the above engineering geological factors influence and control the fracture propagation. The results of the simulation of the fracturing treatment section of the deep shale gas horizontal well by the fracture propagation model are consistent with the micro-seismic monitoring results,which has obvious significance for accelerating the exploitation of difficult-to-exploit resources and guaranteeing the supply of gas resources.