Big Sand Draw Field – The Proof is in the Details

Christopher E. Mullen, Wold Oil Properties, 139 West Second Street, Suite 200, Casper, WY 82601, phone: 307 265-7252, fax: 307 265-7336, [email protected]

The Tensleep production at Big Sand Draw Field, Fremont County, Wyoming, was initiated in 1944. The Tensleep produces 33.6 gravity crude from an average depth of 7500 feet. The average pay thickness is 278 feet, with an average porosity of 2.6%. Since that time more than 54 million barrels of oil has been produced from this reservoir. The Tensleep has seen three distinct phases of development. The first phase took place in the late 1940's to early 1950's. The second phase occurred in the middle 1960's when many of the existing Phosphoria producers were deepened to the thicker, more prolific Tensleep sandstone. The third phase took place in 1972, six additional wells were drill to the Tensleep at this time. Before the drilling of the 1972 program, 43 million barrels of oil had been produced, approximately 79% of the total cumulative production. By studying the location and production histories of these 6 wells three important facts come to light. First, the six wells added 3,300 barrels of oil per day to the field production. Second, two of the six wells had initial production rates in the 2000 barrels of oil per day range. The six wells exhibited higher oil cuts than surrounding wells, indicating the potential for banked oil left in the field. Based on an integrated geologic and reservoir model of the Tensleep at Big Sand Draw it has been determined that there is considerable reserve potential remaining in this 60 year old field.