In the Judy Creek Hydrocarbon Miscible Flood (HCMF) like many other miscible floods, ultimate oil recovery is limited by gravity segregation. This phenomenon is severest in thick vertically permeable sections of the reservoir. Various initiatives have been pursued in Judy Creek to prevent this gravity override, including an effort to identify modifications that could be made to the injection schedule during miscible flooding to improve oil recovery. The Judy Creek HCMF is a staged flood which has been subject to an extensive reservoir surveillance program. Early data interpretation revealed the dynamic nature of the miscible process. Simulation was thereafter employed to examine the dynamics occurring during Water-Alternating-Gas (WAG) flooding and to identify potential recovery enhancements. Previous WAG cycle design procedures used steady state methodology and accepted industry rules of thumb. The use of a simulator permits a more rigorous analysis to optimize WAG cycle parameters such as bank size, cycle time and WAG ratio. Results indicate enhanced performance from high injection rates at low WAG ratios in the early stages of the flood followed by an increased WAG ratio during later solvent injection. Properly sized banks and timing of injected chase gas can optimize oil recovery and injectant utilization. Field production and surveillance data substantiate these results. These modified WAG techniques have been incorporated into the operating strategy of the miscible flood at Judy Creek. As much as 1% incremental recovery in OOIP is anticipated from these refinements to the miscible flood operating strategy. Further development of simpler design methods is required for broader application of these concepts.

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