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Abstract

This paper is a study aimed at the effect of Condensate blockage and tubing size on well deliverability. Gas sales contracts are usually based on the capacity of the system to deliver a specified rate over an agreed period of time. The results of this study are important to determine if a contract can be satisfied or in determining how it can be met. The EOS model is based on data collected from a gas condensate field, offshore Nigeria. This paper highlights the PVT properties most important in predicting gas condensate reservoir behaviour and the approach used in building the EOS model.

Proper EOS characterization is key in modeling the behavior of a gas condensate reservoir. As a starting point, the PVT report is obtained and a material balance analysis is carried out on the reported measured data. The reported data used in the equation of state (EOS) model are the Constant Volume Depletion (CVD), Constant Composition Expansion (CCE) and the hydrocarbon analysis during CVD. These are used in the study to do a material balance analysis based on existing correlations. 

Apart from the subsurface samples, surface samples where obtained and physically recombined, a mathematical recombination was carried out as a quality check on the physical recombination. The material balance serves as a means of validating the PVT data before it is used for an EOS characterization. EOS characterization is carried out using the Soave-Redlich-Kwong (SRK) EOS which in this case is used to fit the measured PVT data through non-linear regression. The heavy fraction i.e. C7+ is split into SCN components from C7 to C30+ before the regression is carried out. In this study the fraction was split into thirty-four components. After a match is obtained, pseudoization is carried out to reduce the number of components in order to reduce simulation run time. EOS characterization is carried out in phazecomp, a state of the art EOS modeling tool. The EOS is tuned so as to match measured data as contained in the PVT report.