The Grieve Unit is in Natrona County, Wyoming, 35 miles west of Casper in the southeastern portion of the Wind River Basin of Central Wyoming. The producing oil reservoir is a stratigraphic trap in the Muddy sandstone which occurs on a monoclinal structure at a depth of 6,900 ft.

This Wyoming "Giant" has produced nearly 28 million barrels of oil since discovery in August of 1954 and presently ranks 20th in the State on a cumulative oil recovery basis. Over 50 percent of the oil-in-place has been recovered. by the various mechanisms including an original gas cap, gas injection, gravity segregation and a strong water drive.

Three submersible pumps are installed in downdip, high water cut wells in order to achieve the higher recovery from gravity segregation. A liquid hydrocarbon plant strips the liquids from the cycling gas production and the products are blended with 36 degrees API crude oil for increased gravity.

Forest Oil Corporation drilled the discovery well in this Muddy sand field and is the Unit Operator with nearly 95 percent working interest. It is estimated that there will be ten more years of crude oil production before gas cap gas blowdown time.

This paper reviews operations and the reservoir properties that have been estimated and calculated.


Presentation of this paper is the result of renewed exploration activities of recent in the Wind River Basin in general, and in the Muddy sand of northeastern Wyoming in the past several years. However, the value of the paper, besides nostalgia for some, should be paper, besides nostalgia for some, should be limited to any permeable, steeply dipping sandstone of the Northern Rockies.

The qualifications of the author are that he was an under-graduate engineer 1,000 miles away during discovery and early life of the Grieve Unit and most of his reservoir work with Forest Oil has been on other reservoirs. Nevertheless, previous reports and records have been reviewed again and Forest personnel that were knowledgeable of the history of the Grieve were interviewed.

This content is only available via PDF.