Measurement and Computation of Near-Critical Phase Behavior of a C1/nC24 Binary Mixture

Abstract

Summary Equations of state (EOS) satisfactorily predict phase behavior and density of reservoir fluids outside the retrograde and near-critical regions. Predictions in these regions, however, are an unresolved problem. A first step to improve the understanding of retrograde and near-critical regions would be to measure the phase behavior of well-defined binary hydrocarbon mixtures of very different molecular sizes. This paper reports measurements on a C1/nC24 binary mixture with a wide retrograde and critical region. Measured dewpoints are in the range of 12, 000 to 15, 500 psia [82.74 to 106.8 MPa]. Retrograde liquid volumes and gas densities at three different temperatures were measured. Liquid phase compositions and densities also were measured on a selective basis. Conventional use of the EOS failed to predict the phase behavior of the model binary system. The data will be useful in modifying the EOS in the retrograde and near-critical regions.