AAPG’s Publishing Legacy Adds New Chapters

AAPG is a science publisher. It’s a tradition that dates back to our founding. And our flagship journal, the BULLETIN, and our special publications are usually a core part of a petroleum geoscientist’s professional library.

Last month was a big one for AAPG science publishing.

AAPG’s associate editors were invited by Elected Editor Steve Laubach to gather in Houston on Feb. 4 to discuss improvements to the BULLETIN’s editorial process, select publication awards and talk about developing a short course for aspiring young authors.

That evening the attendees were inducted into the Charles Taylor Fellowship. The fellowship, named after the BULLETIN’s first editor, Charles H. Taylor, was established by AAPG’s Executive Committee to recognize the vital contributions that all current and former associate editors have made to ensuring that AAPG maintains high standards of published science.

Then on Feb. 7, at a meeting convened by AAPG President Ted Beaumont and SEG President David Monk, my SEG counterpart Steven Davis and I signed a memorandum of understanding for AAPG to join as a partner in the new journal Interpretation.

Interpretation, launched by SEG late last year, is a peer-reviewed quarterly designed to publish papers on the science and practice of interpreting data to better understand Earth’s subsurface, particularly as it relates to the exploration and extraction of resources and for environmental and engineering applications.

This journal fills an important space in science publishing and our participation is the outgrowth of an enhanced and evolving partnership with SEG.

Finally, last month marked the launch of a new BULLETIN feature.

Editor Laubach has been working closely with Beverly Molyneaux, AAPG’s managing editor of technical publications, and Geoscience Director Jim Blankenship to ensure that BULLETIN authors’ manuscripts are published as quickly as possible.

The result is a new website for the BULLETIN and a new feature called Ahead of Print . There you will find manuscripts that have been peer-reviewed and accepted for publication, but have not yet gone through the lay-out and production process.

Ahead of Print gives our members and subscribers the ability to access AAPG science as soon as it’s accepted. This benefits users and is an important step in attracting authors to publish in the BULLETIN.

Ensuring that AAPG remains a relevant and successful science publisher is vital to our long-term objectives. Last month’s activities build upon a strong foundation and position us for the future.

And there are further improvements to come.

I’d like to leave you with one more thought:

Most of us are consumers of the science information published by AAPG. We sift through the online BULLETIN archives and Search and Discovery for papers or presentations that will help us better understand an exploration concept or the geology of a particular region.

That’s great! That’s what these resources are meant to do – to help you do your job better.

But those papers and presentations are only there because someone took the time – usually personal time – to put words on paper, to draft figures and to edit and revise. They probably didn’t do it for fame and fortune (although I wouldn’t dismiss the possibility). Instead they likely saw this contribution as a way to improve their own understanding, to enhance their professional standing and to step into the role of teacher, contributing to the scientific discourse.

They decided to become active participants in advancing our science.

What paper or presentation is locked inside you?

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Director's Corner

Director's Corner - David Curtiss

David Curtiss is an AAPG member and was named AAPG Executive Director in August 2011. He was previously Director of the AAPG GEO-DC Office in Washington D.C.

The Director's Corner covers Association news and industry events from the worldview perspective of the AAPG Executive Director.

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Using diverse geologic and geophysical data from recent exploration and development, and experimental results of analysis of gas content, gas capacity, and gas composition, this article discusses how geologic, structural, and hydrological factors determine the heterogeneous distribution of gas in the Weibei coalbed methane (CBM) field.

The coal rank of the Pennsylvanian no. 5 coal seam is mainly low-volatile bituminous and semianthracite. The total gas content is 2.69 to 16.15 m3/t (95.00–570.33 scf/t), and gas saturation is 26.0% to 93.2%. Burial coalification followed by tectonically driven hydrothermal activity controls not only thermal maturity, but also the quality and quantity of thermogenic gas generated from the coal.

Gas composition indicates that the CBM is dry and of dominantly thermogenic origin. The thermogenic gases have been altered by fractionation that may be related to subsurface water movement in the southern part of the study area.

Three gas accumulation models are identified: (1) gas diffusion and long-distance migration of thermogenic gases to no-flow boundaries for sorption and minor conventional trapping, (2) hydrodynamic trapping of gas in structural lows, and (3) gas loss by hydrodynamic flushing. The first two models are applicable for the formation of two CBM enrichment areas in blocks B3 and B4, whereas the last model explains extremely low gas content and gas saturation in block B5. The variable gas content, saturation, and accumulation characteristics are mainly controlled by these gas accumulation models.

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This article describes a 250-m (820-ft)-thick upper Eocene deep-water clastic succession. This succession is divided into two reservoir zones: the lower sandstone zone (LSZ) and the upper sandstone zone, separated by a package of pelitic rocks with variable thickness on the order of tens of meters. The application of sequence-stratigraphic methodology allowed the subdivision of this stratigraphic section into third-order systems tracts.

The LSZ is characterized by blocky and fining-upward beds on well logs, and includes interbedded shale layers of as much as 10 m (33 ft) thick. This zone reaches a maximum thickness of 150 m (492 ft) and fills a trough at least 4 km (2 mi) wide, underlain by an erosional surface. The lower part of this zone consists of coarse- to medium-grained sandstones with good vertical pressure communication. We interpret this unit as vertically and laterally amalgamated channel-fill deposits of high-density turbidity flows accumulated during late forced regression. The sandstones in the upper part of this trough are dominantly medium to fine grained and display an overall fining-upward trend. We interpret them as laterally amalgamated channel-fill deposits of lower density turbidity flows, relative to the ones in the lower part of the LSZ, accumulated during lowstand to early transgression.

The pelitic rocks that separate the two sandstone zones display variable thickness, from 35 to more than 100 m (115–>328 ft), indistinct seismic facies, and no internal markers on well logs, and consist of muddy diamictites with contorted shale rip-up clasts. This section is interpreted as cohesive debris flows and/or mass-transported slumps accumulated during late transgression.

The upper sandstone zone displays a weakly defined blocky well-log signature, where the proportion of sand is higher than 80%, and a jagged well-log signature, where the sand proportion is lower than 60%. The high proportions of sand are associated with a channelized geometry that is well delineated on seismic amplitude maps. Several depositional elements are identified within this zone, including leveed channels, crevasse channels, and splays associated with turbidity flows. This package is interpreted as the product of increased terrigenous sediment supply during highstand normal regression.

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Field analogs allow a better characterization of fracture networks to constrain naturally fractured reservoir models. In analogs, the origin, nature, geometry, and other attributes of fracture networks can be determined and can be related to the reservoir through the geodynamic history. In this article, we aim to determine the sedimentary and diagenetic controls on fracture patterns and the genetic correlation of fracture and diagenesis with tectonic and burial history. We targeted two outcrops of Barremian carbonates located on both limbs of the Nerthe anticline (southeastern France). We analyzed fracture patterns and rock facies as well as the tectonic, diagenetic, and burial history of both sites. Fracture patterns are determined from geometric, kinematic, and diagenetic criteria based on field and lab measurements. Fracture sequences are defined based on crosscutting and abutting relationships and compared with geodynamic history and subsidence curves. This analysis shows that fractures are organized in two close-to-perpendicular joint sets (i.e., mode I). Fracture average spacing is 50 cm (20 in.). Fracture size neither depends on fracture orientation nor is controlled by bed thickness. Neither mechanical stratigraphy nor fracture stratigraphy is observed at outcrop scale. Comparing fracture sequences and subsidence curves shows that fractures existed prior to folding and formed during early burial. Consequently, the Nerthe fold induced by the Pyrenean compression did not result in any new fracture initiation on the limbs of this fold. We assume that the studied Urgonian carbonates underwent early diagenesis, which conferred early brittle properties to the host rock.

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Although the linkages among surface sediments, geomorphic forms, and hydrodynamics in Holocene ooid tidal sand shoals have been evaluated recently, how these factors are reflected in the geomorphic evolution and stratigraphic record of shoals is less constrained. Yet, such understanding is essential to developing meaningful predictive conceptual models of three-dimensional architecture of ancient reservoir analogs. Integrating remote-sensing imagery, high-frequency seismic data, and core characterization from Lily Bank, a modern tidally dominated Bahamian ooid shoal in which sedimentologic processes are well documented, reveals the stratigraphic record of geomorphic change. An irregular, gently dipping rocky surface (interpreted as the top Pleistocene) with no pronounced topographic high underlies the Holocene oolitic succession. A 6-m (20-ft)–thick poorly sorted, gravelly muddy sand with few ooids overlies this basal surface. This lower interval is overlain by sand with an upward increase in proportion of ooids, sorting, and grain size. The uppermost unit, present only under active bar forms, is well-sorted oolitic medium sand with accretionary foresets. Sediments vary stratigraphically and geomorphically; the lower unit is finer and less well sorted than the upper units, and in the oolitic upper unit, sediment size and sorting on bar crests are distinct from bar flanks. Collectively, these results suggest that a marked antecedent bump is not necessary for occurrence of ooid shoals and that the stratigraphic record of analogous ooid shoal systems may preserve clues of geomorphic position, as well as geobody size and orientation.
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Interpretation of seismic data from the Sorvestsnaget Basin, southwest Barents Sea, demonstrates gradual middle Eocene basin infilling (from the north) generated by southward-prograding shelf-margin clinoforms. The basin experienced continued accommodation development during the middle Eocene because of differential subsidence caused by the onset of early Eocene sea-floor spreading in the Norwegian-Greenland Sea, faulting, salt movement, and different tectonic activity between the Sorvestsnaget Basin and Veslemoy high. During this time, the margin shows transformation from an initially high-relief margin to a progradation in the final stage. The early stage of progradation is characterized by the establishment of generally oblique clinoform shifts creating a flat shelf-edge trajectory that implies a gentle falling or stable relative sea level and low accommodation-to-sediment supply ratio (lt1) in the topsets. During the early stage of basin development, the high-relief margin, narrow shelf, stable or falling relative sea level, seismicity, and presumably high sedimentation rate caused accumulation of thick and areally extensive deep-water fans. Seismic-scale sandstone injections deform the fans.

A fully prograding margin developed when the shelf-to-basin profile lowered, apparently because of increased subsidence of the northern part. This stage of the basin development is generally characterized by the presence of sigmoid clinoform shifts creating an ascending shelf-edge trajectory that is implying steady or rising relative sea level with an accommodation-to-sediment supply ratio of greater than 1, implying sand accumulation on the shelf. This study suggests that some volume of sand was transported into the deep water during relative sea level rise considering the narrow shelf and inferred high rates of sediment supply.

Desktop /Portals/0/PackFlashItemImages/WebReady/evolution-of-shelf-margin-clinoforms-and.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 7965 Bulletin Article