Coupled Fracture-Propagation and Semianalytical Models To Optimize Shale Gas Production

Abstract

Summary With the development of shale gas reservoirs, various fracture-propagation models have been developed to predict hydraulic-fracture geometry by considering the stress-shadow effects. Also, many researchers have been working on the development of various production/simulation approaches to simulate production from the complex fracture geometries. The objective of this study is to combine the fracture-propagation modeling and reservoir simulation to optimize production in shale gas reservoirs. First, we have developed a semianalytical model to simulate shale gas production from the nonplanar-fracture geometry with varying fracture width and fracture permeability along fracture length. The important gas-transport mechanisms such as gas slippage, gas diffusion, and gas desorption are considered. Second, we have developed a fracture-propagation model to predict the nonplanar-fracture geometry by fully coupling elastic deformation of the rock and fluid flow. In this study, the effect of varying number of perforation clusters within a given stage ranging from two to six on the fracture propagation was investigated. Three values of stage spacing were considered including 100, 200, and 300 ft. After predicting the nonplanar-fracture geometry, the semianalytical model is used to simulate production from such fracture geometries. The effects of the number of clusters per stage for varying stage spacing on well productivity were examined. In addition, we compared the well performance with varying stage spacings of 100, 200, and 300 ft under a given lateral length of 2,500 ft. Furthermore, we coupled the fracture-propagation and semianalytical models to analyze a field well performance in a shale gas reservoir. Through the field-case study, a nonplanar-fracture geometry with a good history match was quantified. Also, the difference between the nonplanar-fracture geometry and the converted equivalent planar-fracture geometry with equal fracture length was examined. Finally, the optimal fracture-treatment design for the field well development was recommended. This work can provide new insights into optimization of the number of perforation clusters per stage within a given fracture stage in shale gas reservoirs.