Study on Productivity Evaluation and Performance Prediction Method of Over-pressured, Stress-Sensitive Gas Reservoirs

Abstract

Abstract Forecasting the productivity and performance of overpressured, stress-sensitive gas reservoirs is a major challenge for reservoir engineering. An evaluation method of the effect of stress sensitivity on gas deliverability is presented. This paper introduces a new pressure function, which results from a normalization of the pseudo-pressure and has the dimension of a pressure. Stresssensitive permeability property is taken into account using the permeability modulus. For a practical overpressured, stresssensitive gas reservoir, the gas deliverability is calculated and evaluated. The results show that the decrease degree of gas deliverability is different and it depends on the permeability modulus in the formation on which the gas well is located. And by combining the binomial equation of gas wells with material balance equation, the basic performance prediction model is established. The tank material balance equation for gas reservoirs has been written taking into account the effective compressibility of formation. The optimum is to determine the compressibility in the laboratory using cores from the reservoir under study. An example is given to show the effectiveness of the new method. The calculation results show that the methods presented in this paper are reliable and correct. The model can preferably predict the production performance in the stable production period and the production decline period of overpressure gas reservoir.