Summary
Significant fluid-property variation can be induced with pressure and temperature dynamics in the reservoir associated with oil production. The existing analytical solutions for temperature-transient analysis (TTA) generally assume constant fluid properties, which can be invalid especially for cases of high drawdown and strong temperature signals. In this study, we present a method to account for the fluid-property variations in TTA. The method introduces corrections on fluid-property values as input for analytical solutions, considering the quasilinear behavior of the temporal Joule-Thomson effect on a semilog plot. The corrections are performed on four identified fluid properties in an iterative manner, which can be easily implemented in available temperature-analysis procedures. To validate the developed approach, we model drawdown- and buildup-transient-temperature signals with the fluid-property correction method for nondamaged and damaged reservoirs under different production rates and reservoir-fluid compositions. The analytical modeling results are compared with numerical simulations. In addition, by finding the dominating fluid property, a simplified approach of property correction is presented. Through application to example problems, we show that using the fluid-property correction method presented here can improve the permeability estimations by 60% for the conditions considered in this paper. We present a modified method for damaged reservoirs, which results in an additional 25% improvement on the permeability estimations. With these improvements, the applicability of TTA using analytical solutions can be extended from cases with limited sandface-temperature signals of a few degrees Celsius to stronger signals of 20 to 30°C.
Dynamic object-oriented heat exchanger models for simulation of fluid property transitions
