Well Test Analysis in Near-critical Fluid Reservoirs Using Radial Composite Model with Varying Mobility and Storativity

This paper describes the use of radial composite well test model with varying mobility and storativity to analyse well test data in near-critical fluid reservoirs producing below saturation pressure. Simulated and actual well test data were analysed using this approach. Pressure transient behaviour of near-critical reservoir fluid flowing below the saturation pressure can be described using a radial composite model, with decreasing mobility during drawdowns and increasing mobility during build ups (Sanni and Gringarten, 2008). Published papers have used composite well test models to analyse buildup responses in volatile and condensate reservoirs producing below saturation pressure. However, these papers have not explained how composite reservoir models can be used for combined analysis of drawdown and buildup responses while matching the entire pressure-rate history with a well test interpretation model. Conclusions: -A practical method to analyse well test data in near-critical fluid reservoirs producing below saturation pressure has been presented. The method is based on matching the entire measured pressure with changing mobility and storativity from the different flow periods. -Changing storativity can be modelled using simplified storativity ratio calculation formula, proposed by Aluko, which depends on final flowing pressure; formation volume factors and a fluid characteristic parameter ca.