Case History and Appraisal of the Medicine Pole Hills Unit Air Injection Project
- V.K. Kumar (Koch Exploration Co.) | M.R. Fassihi (Amoco Production Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- August 1995
- Document Type
- Journal Paper
- 198 - 202
- 1995. Society of Petroleum Engineers
- 1 in the last 30 days
- 524 since 2007
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The Medicine Pole Hills Unit (MPHU) Enhanced Oil Recovery project, located in the southwestern corner of North Dakota, is the deepest air injection/in-situ combustion project in the Williston Basin. A unit comprising 9,600 acres with 13 producing wells was formed in July 1985 and air injection operations commenced in October 1987. Laboratory combustion tests and detailed feasibility studies were completed before starting the full scale project. The combination of light oil (390AP1), carbonate formation, hot reservoir (230 F) and low permeability (1-30 md) makes this a unique air injection project. Cumulative air injection as of December 1993 is 12 Bscf.
This paper reviews the production performance of the MPHU to date. Oil production from the unit has shown a significant increase over its historical decline. Additionally, a processing plant has been installed to recover the liquids stripped from the oil by the produced flue gas. Although well workovers, acid tracing and pump changes in some producers complicate the determination of the oil response due to air injection, production decline curve analysis was used to estimate the incremental oil recovery due to air injection. The current air-oil ratio is 8 Mscf/5TB.
Additional topics discussed include the changes in air utilization over time, the benefits of the liquids recovery from the produced gas stream in such a light oil project and an estimate of the field burned volume.
The Medicine Pole Hills field is located near the southwestern flank of the Williston Basin in the southwest corner of North Dakota (Figure 1). The field produces from the Red River carbon-ate formation of Ordovician age that occurs at an average depth of 9500 ft. The Red River is the lowest formation in which widespread commercial production has been found in the Williston Basin and field development on 320-acre spacing was completed in 1978 with the drilling of 18 producing wells and 9 dry holes. The recovery mechanism under primary production was by liquid and rock expansion with a partial water drive. There was little gas produced, so solution gas, gas expansion and gravity drainage are not significant contributors to the drive mechanism. Primary recovery is estimated to be about 15% of the original oil-in-place.
Several enhanced recovery methods have been considered due to the low primary recovery. Waterflooding was ruled out due to anticipated limited injectivities. Repressurization to original reservoir pressure was expected to take more than 10 years with water injection. Natural gas and CO2 injection were ruled out because of the high cost of both gases. Air injection was considered to be a viable alternative primarily because of the successful performance of the Buffalo Field air injection project, located 20 miles south of Medicine Pole Hills field. Both these fields produce from the Red River formation and have similar reservoir characteristics.
The Medicine Pole Hills Unit (MPHU) covering 9600 acres with 13 producing wells was formed in July 1985.
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