The potential for oil and gas development in the greater Wattenberg area (GWA), which lies near the Front Range between Denver and Greeley, Colo., in the Denver Basin, is moderate to high for oil-and-gas-producing formations of Cretaceous age. The potential for development was determined by modeling existing production of oil and gas from these Cretaceous formations and evaluating where the remaining volume of hydrocarbons exceeds estimates of ultimate recovery from existing wells producing from these units. Although areas of varying potential exist for all producing formations, the likely areas of future oil and gas development would be where the potential exists for recovery of additional hydrocarbons from more than one producing formation. The recompletion of existing wells to tap into other formations, for additional oil and gas production, is likely where there is high potential for remaining producible hydrocarbons and especially where a significant number of wells exist. The model reveals that the Front Range project area between Denver and Greeley, Colo., has a high potential for both the drilling of new wells and the recompletions of existing wells. Because this is also an area of rapid and continuing urban growth, decisions regarding future land use will be improved with the understanding of where future oil and gas development could be expected in the Front Range of Colorado.
The greater Wattenberg area, named by the Colorado Oil and Gas Conservation Commission (COGCC) for regulatory purposes to define the prolific oil and gas producing region adjacent to the northern Front Range of Colorado, contains thousands of oil and gas wells producing from rocks of Cretaceous age. The western part of the GWA lies within the study area of the Front Range Infrastructure Resources Project and is just north of Denver, Colo. The most prolific producing formations of Cretaceous age include: (1) the Muddy ("J") Sandstone of the Dakota Group, (2) the "D" Sandstone of the Graneros Shale, (3) the Codell Sandstone Member of the Carlile Shale, (4) the Niobrara Formation, and (5) the Terry and Hygiene Sandstone Members of the Pierre Shale. Based on an assumption that future oil and gas development will proceed apace of petroleum prices and decreases in regulatory well-spacing requirements, a method for determining remaining areas with potential for exploration and production was developed for the GWA. Land planners and others interested in determining land use issues will find it important to understand where these potential areas of oil and gas activity development are located. It is also important to recognize that the Cretaceous-age formations that produce in the GWA fall into both the continuous- and conventional-accumulation classifications used to assess the volume of undiscovered resources (Higley and Cox, this volume). Because volumetric calculations are applicable regardless of accumulation (Craft and Hawkins, 1959), the model is considered applicable to the formations studied.
The online linkage associated with the dataset citation links directly to a website that provides downloadable digital datasets. The online linkage under larger work citation links directly to the publication. http://rockyweb.cr.usgs.gov/frontrange/ is the URL for the Front Range Infrastructure Resources Project homepage.
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U.S. Geological Survey, Box 25046, MS 939, Denver Federal Center
The assumptions outlined here were made prior to developing the model that was used to estimate the future petroleum-production potential in the GWA: (1) volumetric calculations could be used to approximate the initial volume of petroleum in any of the reservoirs of interest in the GWA; (2) decline curve analysis could be used to extrapolate well production into the future; (3) sufficient petroleum remains in the various reservoirs to warrant continued exploration for and development of additional resources. The last assumption was made because exploration continues in the GWA, and the rate of drilling new wells or "recompleting" existing wells is one of the highest in the State of Colorado.
All estimated ultimate recoveries for the present study were generated from monthly production volumes contained in the 1999 PI database (PI / Dwights, 1999). These data are stored by lease for large areas of the United States and were the only oil and gas production data used in this study. Because the production database is proprietary, any well locations shown in this paper for display purposes are from files that are available to the public (Colorado Oil and Gas Conservation Commission, 2001).
well locations
applied petroleum reservoir engineering
petroleum characteristics of the Muddy ("J") Sandstone
production data
U.S. oil and gas assessment
Denver Basin oil and gas assessment
worldwide petroleum production economics
A computer program was written to produce a model for determining remaining potential areas for future oil and gas development in the GWA. For each of the approximately 31,000 160-acre units in the GWA, an initial pore volume containing oil, gas, and water was calculated for each stratigraphic interval. The EUR volume for any producing interval was then deducted from the initial pore volume for that stratigraphic interval in a particular 160-acre unit. The remaining volume is that which would be possible to drain by potential future wells or recompletions of existing wells. Because the location of a well inside a 160-acre unit is not used for any purpose other than just placing it in the proper 160-acre unit, it is probable that some wells could actually drain oil and gas from adjoining 160-acre units or be drained by a large EUR or close wells in nearby units. To compensate for this, the remaining oil-and-gas-filled pore volume was calculated for each of the eight surrounding 160-acre units. The pore volume of the central 160-acre unit could then drain additional oil and gas volumes from these surrounding units or contribute oil and gas to the surrounding 160-acre units. Because the final remaining pore volume value for each 160-acre unit is relative only to a specific producing formation, it was necessary to normalize all of the different producing formations so they could be totaled for a combined analysis. This was done by using a weighted average of each 160-acre unit for each of these formations and then expressing a single value for each 160-acre unit as a percentage of potential of all four formations combined. This percentage of pore-volume potential for each 160-acre unit therefore represents a percentage of remaining potential for all four formations rather than a remaining oil and gas volume. The remaining oil and gas pore volume of a single 160-acre unit was calculated repeatedly, and the model allowed the basic rock properties and water saturations to change with each repetition. The water saturations were varied by 20 percent from the input values, and the contoured stratigraphic thickness was allowed to vary by 10 percent. This was done to account for the fact that no single set of values could accurately represent the rock and water properties in any given 160-acre unit. The final result was the mean of all of the individual model runs. This process was repeated for each 160-acre unit in the GWA. Before the model was run, all wells within each 160-acre unit were counted for the purpose of categorizing each 160-acre unit with respect to its recompletion and drill-down potential. Any single 160-acre unit with high potential for remaining oil and gas resources and a relatively high number of existing wellbores will have a correspondingly high likelihood that some or all of the wells being examined could be used for future production from one or more additional formations. A summary table was then created for each 160-acre unit that contains (1) the well counts, (2) the remaining oil and gas estimate for each formation in the 160-acre unit and (3) the weighted total potential value of all four formations. The data were then viewed on a base map of the Front Range Infrastructure Resources Project study area to determine where areas of moderate or high potential for remaining oil and gas exist within the Front Range Infrastructure Resources Project study area and where such areas coincide with urban areas.
unique identifier
ESRI software
unique cell identifier
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Assigned number that stayed constant through all programs
center-cell X coordinate
center-cell Y coordinate
remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
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remaining areas with potential for exploration and production
USGS
number of wells inside each cell
USGS
Total of available resource, relative to total_sum
USGS
Sum total available for all formations in a given cell, relative to maximum
USGS
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Potential areas of future oil and gas development geographic features
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