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EMD-Related Articles

Bulletin Article

Controls on the deposition and preservation of the Cretaceous Mowry Shale and Frontier Formation and equivalents, Rocky Mountain region, Colorado, Utah, and Wyoming

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

Explorer Division Column EMD By Andrea Reynolds

EMD Will Have a High Profile in Pittsburgh

In my 15 years as an AAPG member, I’ve actively been involved in planning and serving in various roles during AAPG’s Annual Convention and Exhibition (ACE), particularly when I lived in Houston.

Added on 01 May, 2013

Explorer Emphasis Article By Louise Durham

Data Reveals Safety Dynamics For Marcellus

New data presents a new picture of health and safety issues in plays involving the Marcellus Shale.

Added on 01 May, 2013

Explorer Emphasis Article By David Brown

Zagorski Made His Mark With the Marcellus

An affair to remember: Bill Zagorski, the “Father of the Marcellus,” recalls the story of how the now-famed shale play got its start.

Added on 01 May, 2013

Explorer Emphasis Article By David Brown

Author Knows Both Sides of a Controversy

Author Seamus McGraw sees both the upside and downside for the landowner in the development of the Marcellus shale.

Added on 01 May, 2013

Bulletin Article

Modern internal waves and internal tides along oceanic pycnoclines: Challenges and implications for ancient deep-marine baroclinic sands

Thus far, the subject of deep-marine sands emplaced by baroclinic currents associated with internal waves and internal tides as potential reservoirs has remained an alien topic in petroleum exploration. Internal waves are gravity waves that oscillate along oceanic pycnoclines. Internal tides are internal waves with a tidal frequency. Internal solitary waves (i.e., solitons), the most common type, are commonly generated near the shelf edge (100–200 m [328–656 ft] in bathymetry) and in the deep ocean over areas of sea-floor irregularities, such as mid-ocean ridges, seamounts, and guyots. Empirical data from 51 locations in the Atlantic, Pacific, Indian, Arctic, and Antarctic oceans reveal that internal solitary waves travel in packets. Internal waves commonly exhibit (1) higher wave amplitudes (5–50 m [16–164 ft]) than surface waves (2 m [6.56 ft]), (2) longer wavelengths (0.5–15 km [0.31–9 mi]) than surface waves (100 m [328 ft]), (3) longer wave periods (5–50 min) than surface waves (9–10 s), and (4) higher wave speeds (0.5–2 m s–1 [1.64–6.56 ft s–1]) than surface waves (25 cm s–1 [10 in. s–1]). Maximum speeds of 48 cm s–1 (19 in. s–1) for baroclinic currents were measured on guyots. However, core-based sedimentologic studies of modern sediments emplaced by baroclinic currents on continental slopes, in submarine canyons, and on submarine guyots are lacking. No cogent sedimentologic or seismic criteria exist for distinguishing ancient counterparts. Outcrop-based facies models of these deposits are untenable. Therefore, potential exists for misinterpreting deep-marine baroclinic sands as turbidites, contourites, basin-floor fans, and others. Economic risks associated with such misinterpretations could be real.

Added on 30 April, 2013

Bulletin Article

Three-dimensional paleomorphologic reconstruction and turbidite distribution prediction revealing a Pleistocene confined basin system in the northeast Nankai Trough area

Integrated three-dimensional (3-D) paleomorphologic and sedimentary modeling was used to predict the basin architecture and depositional pattern of Pleistocene forearc basin turbidites in a gas hydrate field along the northeast Nankai Trough, off central Japan. Structural unfolding and stratigraphic decompaction of the targeted stratigraphic unit resulted in successful modeling of the paleobathymetry at the time of deposition. This paleobathymetry was characterized by a simple U-shaped paleominibasin. Subsequent turbidity current modeling on the reconstructed paleobathymetric surface demonstrated morphologically controlled turbidity current behavior and selective turbidite sand distribution within the minibasin, which strongly suggests the development of a confined turbidite system. Among three candidate inflow patterns, a northeasterly inflow pattern was determined as most likely. In this scenario, flow reflection and deflection caused ponding and a concentration of sandy turbidite accumulation in the basin center, which facilitated filling of the minibasin. Such a sedimentary character is undetected by seismic data in the studied gas hydrate reservoir formation because of hydrate-cementation–induced seismic anomalies. Our model suggests that 3-D horizon surfaces mapped from 3-D seismic data along with well-log data can be used to predict paleobasin characteristics and depositional processes in deep-water turbidite systems even if seismic profiles cannot be determined because of the presence of gas hydrates.

Added on 30 April, 2013

Explorer Emphasis Article By Louise Durham

Aeromagnetic Data Can Shape Drilling Program

High resolution aeromagnetic surveys are being used with great success in Marcellus shale exploration.

Added on 01 April, 2013

Explorer Emphasis Article By Louise Durham

Study Data Provide New Shale Perspective

A recent study has been completed comparing North American and European shale gas and oil resource systems.

Added on 01 April, 2013

Explorer Emphasis Article By Louise Durham

Study Gives Barnett Shale a Revised Future

Bottoms up! The successful Barnett play is getting a second look, thanks to a new study that took a bottomsup approach to determines areas with the best potential.

Added on 01 April, 2013

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Added on 13 April, 2018

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Added on 05 April, 2023

wwwUpdate Blog By Grant Smith

Free Access to AAPG's Discovery Series 10 and 15 Full Data Set Tutorials

Courtesy of AAPG and AAPG Datapages, two Discovery Series data sets have been donated free of charge for use as online teaching materials. Discovery Series 10 – Sandstone Petrology: A Tutorial Petrographic Image Atlas 2nd Edition and Discovery Series 15 – Carbonate Petrology: Interactive Petrography Tutorial, both authored by Kitty Milliken, have been posted online for easy accessibility.

Added on 11 May, 2020