OF-84-03 Estimated Oil and Gas Reserves for Washington County, Colorado


To most efficiently estimate oil and gas reserves for the State of Colorado, a county-by-county analysis was undertaken. This report is the first 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. 157 pages. Digital PDF download. OF-84-03D

Washington County, located in northeastern Colorado, is approximately 65 miles east of Denver, within the eastern half of the Denver Basin. In this county, oil is produced from the D and J sands, and gas is produced from these same two sands and the Niobrara Limestone. There are 129 fields considered active producers as of December 31, 1982. Of these, 116 are classified as oil fields (based on cumulative gas-oil ratio (GOR) of 15:1). Note that two fields produce (predominantly) oil from one horizon and gas from another (DeNova and Woodrow East). Eleven of the 116 fields produce from both the D and J sands.

Production decline curves are plotted for each currently producing horizon within each field (field-horizon). There are 142 production decline curves plotted, one for each field-horizon. Decline rates were calculated where there were sufficient production histories. Estimated oil reserves for Washington County totaled 29,145,616 barrels. Estimated gas reserve for the county totaled 6,669,086 MCF. 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.