Production Decline Behavior of Shale Gas Reservoirs

The rise in global demand for energy leads oil and gas industry to enhance and develop newer techniques and technologies that produce more oil and gas from resources. Unconventional gas resources comprise a very important share of the domestic natural gas resource base and offer tremendous potential for future reserve and production growth. One of the most important issues associated with shale gas reservoirs is to have an accurate and reliable estimation of the reserves and ultimate recovery. The purpose of this research is to compare different decline curve analysis techniques, it is also to provide a more reliable method for production forecast and reserve estimate for hydraulically fractured horizontal wells producing from gas shale reservoirs. In this study, first, long-term production performance for a variety of well-reservoir systems, including different fracture stages and with and without adsorbed gas cases were simulated. Subsequently, different decline analysis methods were evaluated in employed to predict future performance using the early part of the simulated production history These methods include Conventional Decline Curve Analysis, Weibull Model, and the Power Law Method. The evaluation task was accomplished through quantitative comparison of production forecast results from the decline analysis with the simulated production history. The Power Law Method provided reliable prediction when number of hydraulic fractures was low. However, the Conventional Decline Curve Analysis was found to provide more reliable results in estimating reserves and analyzing production in the cases where the number of hydraulic fracture was high