Productivity analysis of a fractured horizontal well in a shale gas reservoir based on discrete fracture network model
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Treating horizontal wells with massive hydraulic fracturing technology has made shale gas reservoirs economical to develop, and sometimes complex induced fractures are created during the fracturing process. Reports describing fluid flow characteristics in such formations are rare. In this study, a numerical method based on a finite element method (FEM) was developed for productivity analysis of a horizontal well in a shale gas reservoir with complex fractures. The proposed method takes into account the adsorbed gas and complex hydraulic fracture branches. To make the problem more tractable, the dimension of the fracture system is reduced from 2D to 1D based on the discrete fracture network (DFN) model. The accuracy of the new method is verified by comparing its results with those of Saphir commercial software. Finally, the productivity of fractured horizontal wells in shale gas reservoirs with complex fractures systems are obtained and analyzed. Results show that if a well is produced with a constant bottomhole pressure, the well productivity is much greater due to the existence of fracture branches that can increase the stimulated reservoir volume (SRV). In addition, the number of hydraulic fractures (Nf) and fracture half-lengths (Lf) have an important influence on the well’s productivity. The larger the Nf and Lf are, the greater the well productivity will be. The existence of adsorbed gas can markedly improve well productivity, and the greater the Langmuir volume is, the greater the productivity will be. The conclusions drawn by this study can provide guidance for the development of unconventional shale gas reservoirs.
Key wordsfractured horizontal well DFN model FEM productivity analysis shale gas reservoir
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