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Publication Rights Reserved This paper was prepared for the Rocky Mountain Regional Meeting to be held in Montana, June 10–11, 1965, and is considered the property of the Society of Petroleum Engineers. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract A discussion of the oil and water contents and the producing water cut behavior of Tensleep-Minnelusa reservoirs is given. Interpretations of rock and fluid data, logs and well performance are illustrated. Interpretation of the basic data indicates the presence in some reservoirs of oil-water transition zones several hundred feet in thickness. The characteristics of these zones are such that they may have interstitial water saturations as low as 20 per cent of pore space and still produce with extremely high water cuts. These characteristics cause evaluation of productivity of both logs and core analyses to be extremely difficult - particularly in exploration wells where the basic data on the reservoir fluids may not be available. Oil in place values approaching 1000 barrels per acre foot are indicated in zones which may produce at water cuts in excess of 95 per cent. Such productive intervals warrant investigation as secondary recovery prospects using thermal or other advanced techniques. Introduction The Pennsylvanian Age sands, particularly the Tensleep-Minnelusa members, are prolific oil producers in many areas of Wyoming and Montana. Much of this production is low gravity oil and is frequently accompanied by high water cuts. Evaluation of such reservoirs, particularly in exploration drilling has proved to be extremely difficult. Intervals which appear from core analyses and log information to be oil productive have frequently been found to produce at uneconomically high water cuts - either upon initial completion or shortly thereafter. A study of certain measured rock and fluid property information and logs has been made in an attempt to explain this performance and to arrive at better means of evaluation of the productive characteristics of this formation. |
