Experimental study on fracture contribution to gas reservoir permeability and well capacity

Fractures are an important channel for the seepage of reservoir gas. It has an evident contribution to reservoir permeability. However, it is currently difficult to quantitatively evaluate. To solve this problem, an experimental test of gas permeability was carried out after the artificial quantitative fracturing of core. Three factors such as fracture penetration degree, fracture length and width were considered. The contribution of fractures to rock permeability was investigated under two conditions, one where fractures completely penetrate through the rock matrix, and the other in which fractures incompletely penetrate through the rock matrix with penetration degrees of 20%, 40%, 60% and 80%. Both types of fractures contribute to rock permeability. The penetrating fractures increase rock permeability by more than 80%, which is closely related to fracture opening degree (length×width). The nonpenetrating fractures also contribute to rock permeability, by communicating with the matrix and improving reservoir flow. Based on experimental tests, a mathematical model of fracture contribution to single gas well production capacity was established combining three factors:fracture conductivity, fracture communication and matrix gas supply capacity. The fracture contribution to gas well production capacity was estimated using this model together with the basic parameters of actual gas wells.