Strategies for hydraulic fracturing in naturally fractured shale gas reservoir

Abstract

Shale gas reservoirs have become more attractive for the petroleum industry because of the huge amount of reserves. Nanodarcy permeability can be characteristic of shale reservoirs. For this condition, natural gas does not flow economically from the reservoir to the wellbore. Hydraulic fracturing is a common stimulation approach to provide conductive paths through the reservoir so that the gas is allowed to flow more easily hence gas productivity can be improved. Therefore, the objective of this study is to design the hydraulic fracturing strategies in order to improve gas productivity. A horizontal-wellbore production is utilized and the effects of several parameters on the reservoir performance are investigated. These parameters include reservoir porosity, reservoir permeability, fracture spacing, number of fractures, and fracture width. Hydraulic fracturing pattern and gas desorption are also included in sensitivity analysis. The results of this study showed insignificant effect of reservoir porosity but are greatly influenced by reservoir permeability. Increasing the number of fractures can develop gas productivity significantly expressed in linear relationship. Fracture width is another essential factor indicating gas flow ability. However, there is certain point that fracture width cannot further enhance gas productivity. Maximum gas productivity will then be reached at that point. Both the number of fractures and fracture width are the important factors used to design hydraulic fracturing strategies to achieve significant gas productivity improvement.