Unconventional/complex reservoirs

Equation of State Models Phase Behavior of Systems Under Reservoir Conditions

In this work, a perturbed-chain statistical associating fluid theory equation of state has been developed to characterize heavy-oil-associated systems containing polar components and nonpolar components with respect to phase behavior and physical properties.

Figure 3—Flowchart for determining phase behaviour of solvent/water/heavy oil systems with the PC-SAFT EOS.
Flowchart for determining phase behaviour of solvent/water/heavy oil systems with the PC-SAFT EOS.
Source: SPE 218145.

In this work, a perturbed-chain (PC) statistical associating fluid theory (SAFT) equation of state (EOS) has been developed to characterize heavy-oil-associated systems containing polar components [e.g., dimethyl ether (DME) and water] and nonpolar components [e.g., carbon dioxide (CO2) and nitrogen (N2)] with respect to their phase behavior and physical properties. The proposed model shows its superior performance over the widely used Peng-Robinson EOS with a root-mean-squared relative error (RMSRE) of 2.93% for the predicted saturation pressure (Psat) of the aforementioned systems. The theoretical model proposed in this study reproduces accurately experimentally measured phase behavior and physical properties under reservoir conditions.

Introduction

The primary objective of this work is to develop a PC-SAFT EOS to accurately quantify the phase behavior and physical properties of heavy-oil-associated systems consisting of diverse components, including polar elements and nonpolar components. Experimentally, constant composition expansion (CCE) tests have been performed to measure Psat, phase volume, and phase compositions within CO2/heavy oil systems, N2/heavy oil systems, and DME/heavy oil systems in the absence and presence of water.

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