Shale productivity prediction and fracturing optimization based on compositional simulation

Abstract

The reserves of unconventional gas, such as shale and tight gas, is enormous in China. The exploitation of unconventional gas is of significance to secure our nation’s energy future. Precise simulation and prediction of gas flowing behavior in such formations is the key to economic efficiency of exploitation. Different from conventional formations, in shale exist slip flow and gas adsorption. To accurately simulate gas flow in shale, we developed a compositional model based on the hybrid grid which is mainly composed by unstructured PEBI (Perpendicular Bisection) grids. Upon this model, the effects of gas composition, adsorption and slip flow on gas production are analyzed. Horizontal well fracturing in a shale gas reservoir is optimized with the help of this model. The results show that the production of shale gas increases rapidly with the number and effective half-length of fractures, and reaches a plateau when they get large or long enough. Therefore, in order to achieve the maximum economic efficiency, the fracture quantity and effective half-length should be reasonably designed.