Application of Tiab’s Direct Synthesis Technique to Injectivity and fall-off Pressure Transient Test under Non-Isothermal condition
In this study, we present a new analytical solution method that accurately corrects the non-isothermal effects from injection and fall-off tests. The derivative of these solutions is applied to develop the Tiab's Direct Synthesis (TDS) technique. New equations have been developed to determine the different reservoir parameters from pressure injection/fall-off test data. The flow regimes that can occur during an injection test or fall-off test are obtained by separating the different pressure transient time sequences from the analytical solutions. These various flow regimes are also confirmed by analysis of simulated cases for injectivity tests and field examples of pressure fall-off tests. The TDS technique is a method which uses the characteristics of intersection points and slopes of various straight lines from a log-log plot of pressure and pressure derivative data Field and simulated data are interpreted with the conventional methods (Semilog analysis) and TDS technique. There exists a close agreement between the two methods. The result shows that to analyze correctly the pressure transients governed by a moving thermal front, the effects of temperature-and saturation-gradient must be considered. If the fall-off test is not run long enough, the semilog straight line or the second radial line of the derivative plot corresponding to the uninvaded region will not be attained.