Production performance analysis of tight oil/gas reservoirs considering stimulated reservoir volume using elliptical flow

Abstract

Most tight oil/gas reservoirs are naturally fractured with dual-porosity characteristics. After fracturing or re-fracturing, the stimulated reservoir volume (SRV) always exists around the wellbore. This paper demonstrates a composite elliptical mathematical model to analyze the pressure transient and rate transient behaviors in tight oil/gas reservoirs with SRV. This model focuses on two main dual-porosity media regions which are the inner region and outer region divided based on micro-seismic observation. The inner region which has higher flow capacity characterizes the SRV. The inter-porosity flow between matrix and fracture was assumed as unsteady flow for both the inner region and outer region. We solve the model with the elliptical flow model and using Mathieu modified functions, Laplace transform, and Stehfest algorithm comprehensively. The model solution was verified with previous work thoroughly. Also, we presented the pressure transient and rate transient type curves based on which seven flow regimes were recognized including the early wellbore storage period, skin factor period, linear flow period, transfer flow period, first radial flow period, transition flow period, and later radial flow period. Then, effect of four related parameters including SRV size, outer region fracture permeability, fracture half-length, and inner region matrix radius on tight oil/gas transient behavior were investigated. At last, we tested the model with field cases to analyze fractured wells performance in tight reservoirs. History matching results were shown according to real production data and micro-seismic results. The presented model and obtained results can enrich the production performance analysis methods for tight oil and gas reservoirs.