To most efficiently estimate oil and gas reserves for the State of Colorado, a county-by-county analysis was undertaken. This report is the ninth in a series of oil and gas reserve investigations undertaken for those counties in which oil and/or gas was being produced at that time. 34 pages. Digital PDF download. OF-84-11D
La Plata County, located in southwestern Colorado, is partly within the northern San Juan Basin. In this county, oil and/or gas are produced from, in descending order of age, the Kirtland Shale, Fruitland Sandstone, Pictured Cliffs Sandstone, Sanastee Sandstone, Carlile Sandstone, Mancos Shale, Dakota Sandstone, Morrison Sandstone, Ismay Limestone, Paradox Limestone and Hermosa Carbonate. There are 7 fields considered active producers as of September 30, 1983. Of these, one is classified as an oil field (Red Mesa) (based on cumulative gas-oil ratio (GOR) of 15:1).
Production decline curves are plotted for each currently producing horizon within each field (field-horizon). There are 22 production decline curves plotted, one for each field-horizon. Decline rates were calculated where there were sufficient production histories. Estimated oil reserves for La Plata County totaled 2,165,219 barrels. Estimated gas reserves for La Plata County totaled 400,991,767 MCF. Note that the gas reserve calculations are based on a 20-year projection, therefore they do not account for gas production after the year 2002. These figures also do not account for production increases due to secondary and/or tertiary recovery not already in progress, or account for undiscovered reserves, nor do they reflect changes in economics and demand.