Estimation of Reservoir Pressure from the Sensor Data Before and After Injection Tests in Low-Permeability Formations

摘要

One of the most promising and less costly methods to determine formation pressure is pressure curve analysis after injection tests (displacement, minifracturing, DFIT) during hydraulic fracturing. When pressure performance is interpreted after the fracture closure (ACA), for instance, by Nolte method, it is not always possible to diagnose a flow mode (pseudo-linear, pseudo-radial) and to determine formation pressure and reservoir parameters. The paper discusses one the methods of obtaining a "rough" estimate of the formation pressure value in cases with "undertracked" pressure builup curves after frac injection tests. When ACA methods are used to diagnose flow modes after the fracture closure, and when pressure drawdown test is not long enough, it is impossible to determine formation pressure for certain. The paper analyzes bottomhole pressure performance for the time periods before, during and after hydraulic fracturing. The offered approach is an addition to Nolte's (analysis after fracture closure) and Horner's methods. The main advantage of this approach to formation pressure evaluation is that it does not require a complex interpretation or analyzing of bottomhole pressure performance using special software - a visual analysis of the pressure chart received from downhole pressure gauges is enough.