Design and Implementation of a CO(2) Flood Utilizing Advanced Reservoir Characterization and Horizontal Injection Wells in Shallow Shelf Carbonate Approaching Waterflood Depletion

The work reported herein covers select tasks in Budget Phase 11. The principle Task in Budget Phase 11 included in this report is Field Demonstration. Completion of many of the Field Demonstration tasks during the last report period enabled an optimum carbon dioxide (CO{sub 2}) flood project to be designed, economically evaluated, and implemented in the field. Field implementation of the project commenced during late 1995, with actual C0{sub 2} injection commencing in mid-July, 1996. This report summarizes activities incurred following initial project start-up, towards the goal of optimizing project performance. The current project has focused on reducing initial investment cost by utilizing horizontal injection wells and concentrating the project in the best productivity area of the field. An innovative C0{sub 2} purchase agreement (no take-or-pay provisions, C0{sub 2} purchase price tied to West Texas Intermediate (WTI) crude oil price) and gas recycle agreement (expensing costs as opposed to a large upfront capital investment for compression) were negotiated to further improve the project economics. The Grayburg-San Andres section had previously been divided into multiple zones based on the core study and gamma ray markers that correlate wells within the Unit. Each zone was mapped as continuous across the field. Previous core studies concluded that the reservoir quality in the South Cowden Unit (SCU) is controlled primarily by the distribution of a bioturbated and diagenetically-altered rock type with a distinctive chaotic texture. The chaotic modifier is derived from the visual effect of pervasive, small-scale intermixing of tan oil-stained reservoir rock with tight gray non- reservoir rock. The chaotic reservoir rock extends from Zone C (4780`-4800`) to the lower part of Zone F (4640`-4680`). Zones D (4755`-4780`) and E (4680`-4755`) are considered the main floodable zones, though Zone F is also productive and Zone C is productive above the oil- water contact. During Budget Phase 1, the Stratamodel computer program was utilized as the primary tool to integrate the diverse geologic, petrophysical, and seismic data into a coherent three dimensional (3-D) model. The basic porosity model having been constructed, critiqued and modified based on field production and detailed cross-section displays, permeability data was imported into the model, and a 3-D interpolation of the permeability was completed