To most efficiently estimate oil and gas reserves for the State of Colorado, a county-by-county analysis was undertaken. This report is the fourth 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. 168 pages. Digital PDF download. OF-84-06D
Weld County, located in northeastern Colorado, is within the west-central Denver Basin. In this county, oil and/or gas are produced from, in descending order of age, the Sussex Sandstone, Shannon Sandstone, Niobrara Limestone, Timpas Limestone, Fort Hays Limestone, Codell Sandstone, Greenhorn Limestone, Dakota Sandstone, D Sand, J Sand, and the Lyons Sandstone. There are 107 fields considered active producers as of December 31, 1982. Of these, 87 are classified as oil fields (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 141 production decline curves plotted, one for each field-horizon. Decline rates were calculated where there were sufficient production histories. Estimated oil reserves for Weld County totaled 19,022,683 barrels. Estimated gas reserves for Weld County totaled 450,083,794 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.