Abstract

This paper describes the studies which have been completed to evaluate the oil recovery benefits of a carbon dioxide miscible flood of the Judy Creek Beaverhill Lake " A" Pool in Northern Alberta. Subject to all the necessary regulatory approvals, the flood is planned to commence in 1982 with injection of some 1.5 × 106 m3/d of carbon dioxide. Alternate injection of carbon dioxide and water will begin at a ratio of 6:1, with an expected average of 3:1 over the project life. Purchased and reproduced carbon dioxide will be injected into the reservoir to achieve the planned high volumes of carbon dioxide injection of over fifty percent pore volume.

Laboratory tests, including slim tube displacement tests, PVT analysis and a core flood, were conducted to determine carbon dioxide and oil properties along with the characteristics of the displacement process under a carbon dioxide flood. Conventional black oil simulation was used to model a statistical representation of the reservoir with adjustments for reservoir continuity, carbon dioxide dissolution in water, and miscible effects. These results indicated an incremental recovery over waterflood of twenty percent of the original oil in place. The recovery process is aided by a fifty percent swelling effect of the crude oil by carbon dioxide in solution and a crude oil viscosity reduction of forty percent. Also, miscibilityconditions occur down to the bubble point of the oil which is some 8300 kPa below the planned operating pressure.

Introduction

In June 1979, Esso Resources Canada Ltd. applied to the Alberta Energy Resources Conservation Board for approval of a carbon dioxide miscible flood project for the Judy Creek Beaverhill Lake " A" Pool (1). This project is expected to increase the oil recovery by twenty percent of the original oil-in place, with commencement of CO2 injection in 1982. In February 1980, the approval to proceed with theproposed enhanced recovery scheme was received from the Energy Resources Conservation Board.

The Judy Creek Beaverhill Lake " A" Pool, located 250 km northwest of Edmonton, Alberta is an atoll-like reefal limestone complex named the Swan Hills formation and is of Upper Devonian age. This complexconsists of a reef platform and reefal buildup that is subdivided into five stratigraphic units numbered from the base, S1 to S2 (Figure 1). The S1 and S2 units make up the reef platform while the remaining three comprise the reefal buildup and contain most of the oil. The S4 and S5 units have been subdivided into three and two sub-units, respectively, and all units and sub-units are separated by algal or shale beds over large areas of the reef. Geological work has shown that the reservoir is composed of many interbedded lithofacies which have been categorized into three major groups on the basis of rock properties. This categorization when applied to the S4 unit indicates that a significant areal discontinuity exists in the pool and allows for its division into the ‘reef exterior’ and ‘reef interior’ areas (Figure 2).

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