Producing oil from shale oil reservoirs has gained attestations over the past several years. To efficiently and economically develop shale oil reservoirs, the impacts of hydraulic fracture parameters, hydraulic fracture induced complex natural fracture system, and rock characteristics to well performance need to be clearly understood. Numerical simulation based methods provided a better way over other conventional methods for modeling well performance in shale gas reservoirs, however it is still not clear if shale oil reservoir can be modeled using the same ways. We developed a simplified, coarse, dual porosity model to quick evaluate the effectiveness of stimulation treatment and understand shale oil production mechanism. Simulation results of a fine-grid reference model were compared with the simplified model to validate the new methodology. The simplified model greatly decreases simulation time and provides accurate results.

We applied this methodology to Eagle Ford shale oil wells. Historical oil, water, and gas production were matched for selected vertical wells. Reservoir and enhanced zone parameters were obtained after history matching, including OOIP, EUR, porosity and permeability of the matrix and natural fracture system, as well as half length, width, and permeability of the complex fracture network. Sensitivity analyses for horizontal wells then were conducted to quantify the impact of the reservoir characteristics and enhanced zone parameters, including net pay thickness, matrix porosity, permeability of the matrix and natural fracture systems, natural fracture spacing, half length, width, and permeability of the complex fracture network.

The simulation results indicate that the natural fractures permeability has the greatest impact on estimated ultimate oil recovery (EUR). Hydrocarbon pore volume (pay thickness and porosity) have the second greatest impact on EUR. The variability of matrix permeability has little effect on the oil recovery. The simulation results provided insights into effective stimulation designs and flow mechanism for shale oil reservoirs.

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