Countess O and F Pools (T.18, R.15,16w4) are part of a 535 km long Glauconitic compound incised valley system. Between Countess and Alderson, a 90 km reach of this trend has produced more than 100 Mmbbls oil and 300 Bcf gas from 122 pools. Although in its twilight years of production, Countess F Pool was chosen for optimization because it shows below-average secondary recovery (45 %) for this part of the trend. Adjacent O Pool, in contrast, enjoys a 64% R.F. at comparable reservoir parameters. lengthy production and pressure histories, combined with recent 3D seismic, core description, petrology, petrophysics, and detailed sequence stratigraphy have helped refine reservoir models.

F Pool has produced 630 103m3 (4MMbbls) oil during the past 27 years, and currently pumps oil at 38 m3/d(240 bopd) with a 93% watercut. Chert-rich sublitharenites were deposited in fluvially-dominated channels. Seismic amplitude and time slice maps helped unravel a complex pool geometry. Pressure and production vary widely between the resulting compartments suggesting a frontal, "fingering" sweep to the waterflood.

Neighbouring O Pool has produced 909 1Q3m3(5.7 Mmbbls) oil in 22 years of operation. Before optimization, O Pool oil production was 46 m3/d(308 bopd) at a 95% watercut. Well-sorted quartz arenites were deposited in stacked, tidally influenced channels. Pool geometry is simple. Pressure and production history support an interpretation of bottom water drive.

Results of the optimization study predict potential increased recoverable reserves of 500 103m\0.35 Mmbbls) and doubled daily oil production for each pool. Finding and development costs of $2-3/bbl, and 50-70% chance of success make optimization a viable way to balance risk in an oil company portfolio. New exploration leads have evolved from a more detailed understanding of the geological complexity within and between pools. Optimization is a way to breathe new life into mature areas.



About the Author(s)

Lisa A. Griffith is a geologist who received her undergraduate degree from Rice University (Houston), and an M.Sc. specializing in clastic sedimentology from University of Calgary. She has worked in the oil industry for over 15 years, most recently at PanCanadian. Her current interests include unravelling detailed Glauconite channel stratigraphy (with the help of geophysicists, of course!), and finding new ways to use engineering tests and measurements to give insight into the pool architecture. She is a member of the AAPG, CSPG, and APEGGA. Ms. Griffith won "Best Oral Paper" at the 1995 CSPG convention, and recently completed a university tour as "CSPG Visiting Lecturer".



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