Pressure Transient Characteristics of Highly Deviated Wells in Fractured-Vuggy Carbonate Gas Reservoirs

Abstract

AbstractMore and more attention has been paid to the study of flow properties in fractured-vuggy reservoirs because lots of such reservoirs have been found worldwide with significant gas production and reserves. In order to improve carbonate gas reservoir production, highly deviated wells (HDW) are widely used in the field. However, it is very difficult to consider the complex pore structure of fractured-vuggy reservoirs and evaluate the pressure transient behaviors of HDW. This paper presents a semi-analytical model that analyzed the pressure behavior of HDW in fractured-vuggy carbonate gas reservoirs which consist of fractures, vugs and matrix. Introducing pseudo-pressure; Fourier transformation, Laplace transformation, and Stehfest numerical inversion were employed to establish a point source and line source solutions. Furthermore, the validity of the proposed model was verified by comparing with two existing pressure transient models. Then the flow characteristics were analyzed thoroughly by examining the pressure derivative curve which can be divided into five flow stages. The physical meanings of the model parameters were analyzed through sensitivity analysis. Finally, a field case was successfully used to show the application of the proposed semi-analytical model. The study contributes to the highly efficient evaluation of the pressure transient behaviors for HDW in fractured-vuggy carbonate gas reservoirs.KeywordsFractured-vuggy carbonate gas reservoirHighly deviated wellMatrixPressure transient behaviorsWell testing