This paper describes a preliminary reservoir model study for the assessment of tertiary recovery potential by CO2injection in a watered-out Viking sand unit of central Alberta, Canada. A typical- pattern approach based on average reservoir properties and completely watered- out initial conditions is taken to provide a quick evaluation of the tertiary CO2 process. This simplified approach is deemed necessary before any considerable efforts are expended in the detailed engineering, geological and laboratory evaluations. Several one-, two- and three dimensional miscible model runs are made to investigate the effects of gravity segregation, flood pattern, injection sequence, well spacing and total CO2 volume injection. Computer results indicate that significant amount of tertiary oil is recoverable from a five-spot pattern by CO2 injection with well spacing as large as 80 acres and total CO2 injectionas small as 25 percent original hydrocarbon pore volume. Finally, a reservoir parametric sensitivity study is conducted to investigate the possible impact of various reservoir parameters on the tertiary CO2 flood performance
Despite considerable efforts expended in the development of tertiary oil recovery technology in the United states, very limited effort has been expended in Canada. In view of the rapid decline of conventional oil reserves in Alberta and the interest expressed by both the federal and provincial governments in achieving energy self-sufficiency in the future, it is timely to participate early and actively in the planning and evaluation of potential tertiary recovery schemes to increase recovery from known hydrocarbon accumulations.
The injection of carbon dioxide (CO2) into oil reservoirs has been shown to be capable of recovering significant amounts of additional oil after waterflooding l – 3. The CO2 process has been field tested in many reservoirs and numerous laboratory 4–7 and simulation studies 8 – 12 have been reported in the literature which enhance the understanding of the recovery mechanisms in a CO2 flood.
Normally prior to any detailed technical studies, pre-screening of reservoirs for proper selection of candidates followed by a preliminary technical and economic feasibility study is usually performed to provide a quick assessment of the CO2 tertiary recovery potential of a chosen reservoir. Reservoir simulation models have been widely used for these purposes. A careful review of the past production history and reservoir description of the Joffre Viking oil reservoir indicated many positive features making it amenable to CO2 flooding. The objectives of this preliminary feasibility study were to assess the tertiary recovery potential of CO2 injection in the Joffre Viking reservoir with the use of a miscible reservoir simulator and to investigate by a reservoir parametric sensitivity analysis the possible impact of various reservoir parameters on the CO2 Flood performance.
The Joffre Viking oil reservoir, located immediately east of Red Deer in south-central Alberta (Figure 1), was discovered in July, 1953 by the drilling of Canadian Superior Unit Morton No. 9-19-3825 W4M exploratory well. The field is approximately 37 km (23 miles) long and up to 2 km (1.5 miles) in width.