REACTIVATION OF AN IDLE LEASE TO INCREASE HEAVY OIL RECOVERY THROUGH APPLICATION OF CONVENTIONAL STEAM DRIVE TECHNOLOGY IN A LOW DIP SLOPE AND BASIN RESERVOIR IN THE MIDWAY-SUNSET FIELD, SAN JOAQUIN BASIN, CALIFORNIA

A previously idle portion of the Midway-Sunset field, Aera Energy's Pru Fee property, has been brought back into commercial production through tight integration of geologic characterization. geostatistical modeling, reservoir simulation, and petroleum engineering. This property, shut-in over a decade ago as economically marginal using conventional cyclic steaming methods, has a 200-300 foot thick oil column in the upper Miocene Monarch Sand. However, the sand has a shallow dip (about o0), thus inhibiting gravity drainage, lacks laterally continiositse am barriers within the pay interval, and has a thick water-saturated transition zone above the oil-water contact. These factors have required an innovative approach to steam flood production design that balances optimal total oil production aims economically viable production rates and performance factors, such as OSR and OWR. The methods used in this DOE Class I11 oil technology demonstration are accessible to most operators in the Midway-Sunset field and could be used to revitalize properties with declining recovery of heavy oils throughout the region. In January 1997, the project entered its second and main phase with the purpose of demonstrating whether steamy flood can be an effective mode of production of the heavy, viscous oils from the Monarch Sand reservoir. A steamy flood pilot consisting of four 2 acre nine-spot patterns was developed in the center of the property and put on line. During 1998, ARC0 Western Energy drilled 37 additional wells on the property outside of the steam flood pilot and began producing them by cyclic steamy injection. In January 2000, the new operator of the property, Aera Energy LLC, converted all 37 cyclic wells into ten additional nine-spot steam flood patterns that flank the original DOE pilot on the south, west and north. To convert from cyclic to steam flood Aera Energy LLC drilled 10 additional injectors and three additional temperature observation wells on the property. The only portion of the property not now in steam flood is the very southeast comer where the Monarch Sand pay is less than 200 ft thick. The objective of the project is not just to commercially produce oil from the Pru Fee property, but rather to test which operational strategies best optimize total oil recovery at economically acceptable rates of production volumes and costs. As of March 2001, after 49 months of steam flood production of the four-pattern pilot and 30-35 months of cyclic/steam flood production of the surrounding 10 patterns, the total cumulative production of oil from the Monarch Sand stands at 1,066,192 bbls. More than half (562,366 bbls) of that oil was from the four-pattern Pru Fee steam flood pilot; the remainder was from 10-pattern array formed by wells drilled in 1998. Steam flood design principles developed and demonstrated for this project now have been adopted with dramatic oil recovery improvement in an adjacent lease in the southern Midway-Sunset field.

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