Abstract

The partial differential equations governing immiscible carbon dioxide drivefor moderately heavy oil have been developed for partial equilibrium among thegas, oil and water phases. Different sets of scatting criteria, based on the afore mentioned partial differential equations, have been developed. In order toconstruct scaled models with different operating conditions.

A set of similarly groups are derived by dimensional and inspectional analysesfor the displacement of moderately heavy 0il by carbon dioxide with partialequilibrium. New dimensionless groups for the interface mass transferparameters were obtained. Different sets of scaling criteria are derived and Compared

Introduction

Immiscible CO2 flooding for moderately heavy oil is an importantrecovery method for thin, marginal or otherwise poor heavy oil reservoirs, thatare unsuitable for thermal recovery methods. Up to now, the only high pressurescaled model for this process has been reported by Rojas (1).

Farouq Ali and Rojas (2) presented carbon dioxide/brine injection strategiesfor heavy 0il recovery From thin formations. Experiments were conducted in ascaled model with Alberfeldy-Lloydminster heavy oils (1000 - 5000 mPa.sl. usinga small slug (20% hydrocarbon pore volume) of subcritical carbon dioxide in arectangular scaled model, designed to Simulate a thin format ion.

They reported that the Injection of alternate slugs of carban dioxide (at 5.5MPa & 21–23 C) and brine (the WAG - Water Alternating Gas-process) yieldedthe best results: highest incremental recovery and lowest carbon dioxiderequirement. It was found that a high rather than a low WAG ratio should beused in the field. The oi1 recovery can increase up to 48% of the oil-in-place.An increase in oil viscosity caused a reduction in oil recovery and an increasein carbon dioxide requirements.

Scaling of the immiscible CO2 flooding for moderately heavy oil withpartial equilibrium among oil, gas and water phases is the aim of thispaper.

LITERATURE REVIEW

Background to Scaling Immiscible CO2 Flooding

A set of scaling groups were derived by Rojas (1) using dimensional andinspectional analyses for the displacement of heavy 0il by carbon dioxide andwater assuming that instantaneous equilibrium was attained in thereservoir.

After relating the capillary and diffusive forces, and considering that modeland prototype have the same mortology, the same fluids, and are operated at thesame conditions of pressure and temperature the following scaling groups werecompletely satisfied Geometric factors: Mortology factor: Ratio ofgravitational to VISCOUS Forces: Water-gas ratio of slug volumes, when amoderate Injection rate for CO2 brine floods was used.

Background to the Nonequilibrium Processes

When mass transfer is considered in a reservoir model. It is assumed that localinstantaneous equilibrium is attained in the reservoir under all conditions.But there is a need to consider interfacial mass transfer that occurs whencarbon dioxide is injected into a heavy 0il reservoir, since initially, theyare not in thermodynamic equilibrium, and mass transfer phenomena occur.

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