Sensitivity Analysis and Stochastic History Matching of Shale Gas Production Based on Embedded Discrete Fracture Model

Abstract

Accurate description of fracture system is the crucial to predict the production characteristics of shale gas reservoir. In order to improve the accuracy and effectiveness of production evaluation, an embedded discrete fracture model (EDFM) is used to simulate the shale gas production. It can consider the Knudsen diffusion, non-Darcy flow, and non-instantaneous desorption. To investigate the effects of key parameters on the production, the sensitivity of these parameters is analyzed through orthogonal test analysis, which includes the fracture density, half-length, orientation and flow conductivity of primary hydraulic fractures and secondary hydraulic fractures, and the permeability of matrix. After the determination of the sensitive parameters, the ensemble Kalman filter (EnKF) method is used to conduct history matching and predict the production characteristics. Sensitivity results show that permeability of matrix, the number of hydraulic fracturing stages, the conduction of the primary hydraulic fractures, and the half-length of the secondary hydraulic fractures are key parameters affecting the shale gas production. The cumulative gas production is positively proportional to these parameters. The increasing ratio of cumulative gas production starts to decline when the permeability of primary hydraulic fractures reaches 0.001 mD. Before the secondary hydraulic fractures are connected, the cumulative gas production increases with the half-length of the secondary hydraulic fractures. The accurate characterization of these key parameters in the fracture system of shale gas reservoir can be achieved through history matching.