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CHIDSEY, THOMAS C., JR., Utah Geological Survey, Salt Lake City, UT; and DAVID E. EBY, Eby Petrography & Consulting, Inc., Littleton, CO

Abstract: Mule Field in the Paradox Basin of Southeastern Utah: A Case Study for Small Carbonate Buildups, Horizontal Drilling, and Carbon Dioxide Flooding

Mule field is an excellent example of a small carbonate buildup reservoir in the shallow-shelf/shelf-margin facies of the Desert Creek zone of the Pennsylvanian (Desmoinesian) Paradox Formation, Paradox basin, southeastern Utah. As part of a five-field, DOE-sponsored Class II Oil Study of secondary/tertiary recovery techniques, it was the first field in the basin (outside of Greater Aneth field proper) to be tested with a horizontal well, and is considered a candidate for CO2 flooding.

Mule field was discovered in 1991 and consists of two wells: Mule No. 31-K-1 (N) and Mule No. 31-M. The main producer, Mule No. 31-M, had an IPF of 735 BOPD and 97 MCFGPD. The reservoir consists of a mud-free, phylloid-algal buildup (mound) with moundflank detrital deposits. The principal reservoir rocks are porous algal-lime bafflestones and crinoidal packstones containing dolomitized zones interbedded with low-permeability wackestones, mudstones, and dolomites. Incomplete dolomitization and secondary anhydrite replacement have resulted in poor reservoir properties in some intervals.

Mule field is a linear buildup, 0.5 miles long and 900 feet wide. Additional reservoir potential to the northeast was tested with a horizontal well. The well initially flowed 149 BOPD through 939 horizontal feet of lagoonal and mound-flank deposits, having missed the targeted core of the phylloid-algal mound.

Cumulative production from Mule field is 403,677 BO and 0.26 BCFG as of September 1, 1998. Estimated primary recovery from the field is 454,000 BO and 0.3 BCFG. Based on modeling/simulation of similar fields in the basin, CO2 flooding could recover 72% of the remaining 1,546,000 BO in place, principally from the high-storage but low-flow-capacity upper section of the reservoir.

AAPG Search and Discovery Article #90919©1999 AAPG Rocky Mountain Section Meeting, Bozeman, Montana