Regional variations in thickness and facies of clastic sediments are controlled by geographic location within a foreland basin. Preservation of facies is dependent on the original accommodation space available during deposition and ultimately by tectonic modification of the foreland in its postthrusting stages. The preservation of facies within the foreland basin and during the modification stage affects the kinds of hydrocarbon reservoirs that are present.
This is the case for the Cretaceous Mowry Shale and Frontier Formation and equivalent strata in the Rocky Mountain region of Colorado, Utah, and Wyoming. Biostratigraphically constrained isopach maps of three intervals within these formations provide a control on eustatic variations in sea level, which allow depositional patterns across dip and along strike to be interpreted in terms of relationship to thrust progression and depositional topography.
The most highly subsiding parts of the Rocky Mountain foreland basin, near the fold and thrust belt to the west, typically contain a low number of coarse-grained sandstone channels but limited sandstone reservoirs. However, where subsidence is greater than sediment supply, the foredeep contains stacked deltaic sandstones, coal, and preserved transgressive marine shales in mainly conformable successions. The main exploration play in this area is currently coalbed gas, but the enhanced coal thickness combined with a Mowry marine shale source rock indicates that a low-permeability, basin-centered play may exist somewhere along strike in a deep part of the basin.
In the slower subsiding parts of the foreland basin, marginal marine and fluvial sandstones are amalgamated and compartmentalized by unconformities, providing conditions for the development of stratigraphic and combination traps, especially in areas of repeated reactivation. Areas of medium accommodation in the most distal parts of the foreland contain isolated marginal marine shoreface and deltaic sandstones that were deposited at or near sea level lowstand and were reworked landward by ravinement and longshore currents by storms creating stratigraphic or combination traps enclosed with marine shale seals.
Paleogeographic reconstructions are used to show exploration fairways of the different play types present in the Laramide-modified, Cretaceous foreland basin. Existing oil and gas fields from these plays show a relatively consistent volume of hydrocarbons, which results from the partitioning of facies within the different parts of the foreland basin.
Added on 31 May, 2013
January and early February are going to be busy months for AAPG’s Distinguished Lecture program, with several speakers set to make tours.
Added on 01 January, 2015
Three speakers from the AAPG-AAPG Foundation’s Global Distinguished Lecture Program will be on tour in November, making stops in the western parts of North America and throughout the Asia-Pacific Region.
Added on 01 November, 2014
EIA's Petroleum Supply Monthly report shows oil production in the lower 48 states has increased over the last three years.
Added on 01 July, 2013
Explorer Director’s Corner
As this issue of EXPLORER goes to print, geoscience students and industry recruiters are gathering on the plains of Wyoming for the Rocky Mountain Rendezvous, the annual job fair of AAPG’s Rocky Mountain Section.
Added on 01 October, 2014
Explorer Division Column EMD
Every six months, chairs of the Energy Minerals Division committees convene and report on developments in the areas they cover. In this column, we highlight important observations from these recent reports.
Added on 01 February, 2014
At the start of the now-phenomenal shale play bonanza, the thinking in general was that the rocks were homogeneous across an area of interest. Then reality set in as the shale E&P players came to realize via the drill bit that heterogeneity rules, and homogeneity and uniformity are not even bit players in the big picture.
Added on 01 July, 2014
The “Converting Technology Into Dollars” panel will explore how top-tier organizations lead the way by rapidly improving and deploying unconventional resource technologies and incorporating new learnings across their organizations.
Added on 01 July, 2014
This year, URTeC has added an enhanced preview of “Coming Attractions.” In addition to looking at established plays, URTeC will provide significant information about emerging unconventional resource possibilities in North America and around the world.
Added on 01 July, 2014
The EXPLORER interviews Colorado Gov. John Hickenlooper and others about presiding over the national nexus of energy and environmental politics.
Added on 01 June, 2014