An Efficient Reservoir Simulation Approach to Design and Optimize Unconventional Gas Production

Abstract

Abstract Shale gas production has gained worldwide attention over the past several years. Production from shale gas reservoirs requires horizontal drilling with multiple hydraulic fracturing to obtain the most economical production. However, there are high cost and uncertainty due to many inestimable and uncertain parameters such as reservoir permeability, porosity, fracture spacing, fracture half-length, fracture conductivity, gas desorption, geomechanics and existing natural fracture. Therefore, the development of a method quantifying uncertainties and optimization of shale gas production in an efficient and practical way is clearly desirable. In this paper, we present a user-friendly and efficient framework to obtain the optimal gas production scenario by optimizing the uncertain factors by integrating several commercial simulators, an economic model, Design of Experiment (DoE), and Response Surface Methodology (RSM) with a global optimization search engine. Specifically, we use factorial design to screen insignificant factors and find the most influential design and uncertain factors, and then employ RSM to design over those most influential factors to fit a response surface using net present value (NPV) as the objective function, and finally identify the most economical production scenario under conditions of uncertainty. Eight uncertain parameters, such as porosity, permeability, reservoir thickness, reservoir pressure, bottom hole pressure (BHP), fracture spacing, fracture half-length, and fracture conductivity with a reasonable range based on Barnett Shale information are investigated. Also, different gas prices are considered for the optimization process. This framework is effective and efficient for hydraulic fracturing treatment design and production scheme optimization in unconventional gas reservoirs. It can contribute to providing guidance for engineers to modify the design of a hydraulic fracture treatment prior to the actual fracture treatment.