Propagation area evaluation of hydraulic fracture networks in shale gas reservoirs

Abstract

Based on hydraulic fracturing experiments in laboratory, the hydraulic fracture propagation in shale is analyzed, a method for evaluating the fracture propagation extent is proposed, and the effects of geological factors and engineering factors on fracture propagation are studied. “Stimulated Rock Area (SRA)” is proposed as an evaluation index for the hydraulic fracturing results. By analyzing the experiment results, it is found that hydraulic fracturing in shale reservoirs can generate a complex fracture network; a lower stress difference in brittle shale formation and a shorter distance between hydraulic fracture and bedding plane lead to a larger SRA and more complex fracture geometry; a fracture network is more likely to generate in the case that the angle between horizontal maximum stress direction and bedding plane is 90° or large enough, or the approaching angle between hydraulic fracture and well-opened natural fracture is close to 90°; a higher brittle mineral content leads to better fracturing ability; low fluid viscosity and high flow rate lead to a large SRA; a variable flow rate increases the possibility that the hydraulic fracture communicates with bedding planes and natural fractures. Key words: shale, hydraulic fracturing, fracture propagation, fracture network, stimulated rock area, rock mechanics, reservoir stimulation