Abstract

A new method is presented that can be used to predict molal specific volumes of equilibrium states as a function of reduced pressure. The reduced pressure for pressure. The reduced pressure for multicomponent systems, in turn, is defined as the ratio of the operating pressure divided by the convergence pressure as determined by the Critical Composition Method. This technique essentially extends the law of corresponding states to include multicomponent systems that exist in a two-phase region of phase space. Published experimental data is used to justify Published experimental data is used to justify this extension.

This method was first programmed into a phase routine to determine how accurately it phase routine to determine how accurately it would predict experimentally determined liquid saturations obtained by constant volume expansion of a volatile reservoir fluid. Experimental and predicted results were found to be in very close agreement.

After this approach was verified, this technique was then incorporated into a Modified Muskat analysis to predict recovery from a volatile oil reservoir.

Introduction

The U.S. is currently faced with an energy shortage that has resulted in deep-well exploratory drilling (in excess of 30,000 ft.). At these greater depths, reservoirs are more likely to contain volatile fluids since the reservoir pressure and temperature are higher than normally encountered at more shallow depths. Therefore, due to the nature of these fluids, the ability to calculate reservoir performance and thus predict recoverable performance and thus predict recoverable reserves will require the accurate determination of their phase compositions and accurate predictions of the densities of equilibrium liquid predictions of the densities of equilibrium liquid and vapor phases. The phase composition calculation is based on mass conservation, while an accurate phase-density calculation is necessary for the conservation of pore volume.

This paper presents a method for predicting volatile oil recovery that incorporates predicting volatile oil recovery that incorporates both of these conservation principles by utilizing the thermodynamic properties correlated as a function of convergence pressure, temperature, and pressure. One of the potential advantages of such an approach lies in applications to non-equilibrium displacement of a liquid by a gas phase.

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