New rate-decline forecast approach for low-permeability gas reservoirs with hydraulic fracturing treatments

Abstract

Estimating production in low-permeability gas reservoirs accurately has been of more concern to oil and gas industries in recent years. Until now, various techniques to estimate well production have been developed. Among them, decline curve analysis models have been recognized as the most efficient and easiest approach to be applied. Unfortunately, each decline curve model has its own limitation and will not allow us to forecast production in low-permeability gas reservoirs with confidence. In this paper, firstly, the review of Arps, stretched exponential production decline (SEPD), and Duong methods is conducted explicitly to illustrate the reasons resulted in their limitations. Subsequently, a new empirical decline model with two fitting parameters is developed based on the proposed linear relation of logarithmic production versus the product of square root of time and logarithmic time, which takes the change of decline exponent with production time into account. In addition, a detailed procedure applying this novel decline model for low-permeability gas wells is presented, which is reliable and easy to be utilized. Furthermore, this new model is validated by numerically simulated cases and field observations, which appears good match between forecast rates calculated by this proposed method and numerically simulated rates/field rates. The comparison between this novel method and several traditional methods are further conducted, which indicates that this new approach leads to more reliable forecast than commonly utilized approaches. This work should provide a theoretical guidance to assist analysts in estimating hydrocarbon production rapidly and efficiently in low-permeability reservoirs.