The Rainbow Keg River B Pool, an atoll reef of Middle Devonian Age, is divided by a saddle into northern and southern lobes. Oil product; on fromthe subject pool began in 1965 and primary depletion continued unti1 a waterflood pressure maintenance scheme was instituted in 1968. Currently the oil/ water interface is above the highest point of the saddle and the unswept oil zones of the two lobes are now physically separated.

As a first step, a hydrocarbon miscible scheme is being implemented in the northern lobe to recover the oil above the present oil/water interface. This paper discusses the laboratory and simulationstudies performed to design this scheme.

Conditions of first contact miscibility were established using slim tube displacement tests, ternary phase diagram, prediction of miscibility correlations and by comparison with other Rainbow Keg River Pools under hydrocarbon miscible process. The poolwas represented in a 3-dimensional cartesian grid system, from which the waterflood history match was obtained. A number of solvent coning studies were also performed to generate correlation tables incorporated into the model. A relatively new technique was used to establish the dispersion coefficients at the solvent/oil interface by history matching the geologically similar Keg River H Pool. The casesstudied included continuous solvent injection, bank size sensitivity, rate sensitivity and the effectsof various infill drilling strategies on oil and solvent production.

The coning and cusping phenomena were found to be dominant over the diffusional aspects. It was established that infill drilling could improve the volumetric sweep efficiency subject to rate constraints.


The Rainbow Field, located in northern Alberta, Canada (Figure I), was discovered in 1965. The Keg River 8 Pool, which is an atoll reef structure, is the largest oil accumulation in the Rainbow Field (Figures 2 and 3). In 1968. water injection was initiated into the 8 Pool aquifier displacing the all vertically. This recovery mechanism has only recently been discontinued in the northern lobe, but is still in progress in the southern lobe.

For the past two years, studies have been performed to evaluate the performance of the waterflood and the feasibility of a hydrocarbon miscibleflood.

This paper summarizes the laboratory and simulation studies, which have led to the initiation of a hydrocarbon miscible flood in the north lobe of the pool. Figure 4 is an enlarged gross pay map of the north lobe. The laboratory work included slim tube displacements and PVT cell studies. The objectives of the simulation work were the evaluation of the ultimate recovery under the exist1ng waterflood as well as a hydrocarbon miscible scheme, coning tendencies, infi1l drilling and solvent bank size.


The Rainbow Keg River B Pool is made up of four main depositional environments. Sequentially from the bottom to the top there is an organic reef, a transition zone from organic reef to shallow lower shoal, a shallow lower shoal and a shallow upper shoal (Figures 5 to 7).

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