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Abstract

The Wilmington Steamflood of Union Pacific Resources Co. (UPRC) at Long Beach, CA was initiated in 1989, in a previously waterflooded reservoir. Average initial reservoir oil saturation, at the start of the steamflood was 35%.

Field production data were studied, to derive an overall energy balance for the steamflood to calculate the steamflood capture efficiency and predict further steamflood performance. Heat-losses due to produced fluids were calculated. Predicted production schedules from the model were history-matched with field production data.

All steamflood calculations were carried out using a PC-based spreadsheet program. The major results were as follows:

  • The capture efficiency of the Wilmington steamflood was calculated at 60%. This is an acceptable value, taking into account the fact that the reservoir had previously been waterflooded to a low oil saturation of 35%. - The calculated heat balance showed a high heat-loss, not only to adjacent formations, but also through produced fluids. Of the cumulative heat injected up to the time of the study, 21% had been lost to vertical conduction and 21% through produced fluids.

  • Predicted production schedules indicated that up to 43% of the oil in place (at steamflood initiation) would be recovered by the steamflood.

WILMINGTON STEAMFLOOD

The Wilmington Oil field, Los Angeles County, California is the third largest in the U.S., after Prudhoe Bay and the East Texas fields, on the basis of cumulative oil production, with a total of 2.4 billion barrels produced. A good description of the initial pilot steam flood carried out by UPRC in this field from 1982-1989 is given by Lim et al., 1993. The pilot 20 acre steamflood is now part of the main 130 acre Wilmington Steamflood. The portion of the field studied had initially been waterflooded to a low oil saturation of 35% before the main steam flood was initiated in 1989.

The steam flooded reservoir is unconsolidated sandstone in the Tar Zone (T, D1 and D3 members) with average gross and net thicknesses of 170 feet and 128 feet respectively. Average reservoir pressure was estimated at 350 psig in 1993. The steam flood project has a surface pattern area of 129.73 acres divided into approximately 17 individual seven-spot patterns, each of 7.5 acres. Average well depth is 2500 feet. The oil in place at steam flood initiation was calculated at 18 million barrels with a movable oil volume of 12.9 million barrels, assuming an initial oil saturation, Soi, of 35% (at steam flood initiation), a final oil saturation Sor of 10% and an average porosity of 40%.

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