Petroleum Drilling Techniques, Issue 4, 2018

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Study of a Simulation of Degree of Fracturing Production and Resulting Gas Flow in Shale Gas Reservoirs


Due to small pore throats and low permeability of shale reservoirs, primary natural fractures and induced fracture networks hydraulic fracturing can dramatically aggravate the complexity of shale gas flow. We needed to accurately characterize the pseudo-steady seepage characteristics of shale gas. To do so, we proposed a mathematical characterization method using discrete fractures coupled with a multiple continuous media system. Taking into consideration the distribution of reservoir fractures, the commercial numerical simulator was used to establish the discrete fractures and to couple them with multiple continuous media took into consideration adsorption/desorption for shale gas reservoirs. The mathematical model incorporated a local grid encryption method to describe the discrete fracture network. Based on the established multi-continuum system mathematical method, it was possible to model induced fractures within the natural fractures, including densely distributed micro-crack system that formed after fracturing. By using the established model, it was possible to systematically analyze the effects of fracture parameters, such as lateral/longitudinal mobilization of reservoirs, fracture conductivity, fracture half-length, and fracture arrangement on shale gas drainage area and gas well productivity. Studies revealed that increasing the reservoir stimulation volume could significantly increase shale gas production per well. Above all, the configuration relationship between the main fracture and the secondary fracture network should not be ignored. The model demonstrated that under the same reservoir stimulation volume, the connectivity between the fracture and wellbore was a necessary condition for increasing shale gas production, and it should be maximized. Studies suggested that the new modeling technique is effective and that it can be used as a guide when designing shale gas fracturing stimulation.