Analysis of Production Data with Elliptical Flow Regime in Tight Gas Reservoirs

Abstract

Abstract Analysis of production data for tight gas reservoirs is based on pressure transient (PT) analysis, which is now a conventional procedure for fractured tight gas reservoirs. Key parameters can be estimated during the analysis: fracture conductivity, fracture half-length and reservoir properties. Most PT analysis methods deal with bilinear, formation linear, and pseudo-radial flow regimes. It is well known that an elliptical flow regime can appear between formation linear and pseudo-linear flow regimes. Sometimes the period is very short and cannot be identified. But there are many cases when only formation linear and elliptical flow regimes are present in production data records and the time needed to reach the pseudo-radial period is more than decades. Most PT analysis methods substitute elliptical flow regime for pseudo-radial, which may lead to the incorrect calculation of key parameters of reservoirs and fractured wells. In this study, we present the development of an approach for elliptical regime analysis in the production data record for calculation of key parameters of finite-conductivity fractured wells and reservoirs: fracture conductivity, fracture half-length, reservoir permeability, and effective drainage area. This method uses an analytical equation for elliptical flow period and estimation of parameters from the equation. The development is based on more stable deconvolution analysis of production data with variable rate/pressure and more reliable analysis of response function after deconvolution. We present here some synthetic and field cases to demonstrate the results of calculations.