In this month’s AAPG BULLETIN...
February 2012
A new oil-window indicator? The magnetic assemblage of claystones from the Baffin Bay volcanic margin (Greenland)
Magnetic minerals can indicate burial temperature
The two types of magnetic assemblages of Cretaceous claystones from the western volcanic margin of Greenland may be indicative of low-grade burial below and within the oil window. These results compare well with claystones from the Paris basin and the Jura Mountains.
Carbonate porosity creation by mesogenetic dissolution: Reality or illusion?
Evidence is lacking
Significant volumes of porosity are unlikely to be created by deep burial dissolution in carbonate reservoirs as this model is unsupported by empirical data and violates important chemical constraints on mass transport. Pore waters are typically saturated and buffered by carbonates.
Probabilistic correlation of single stratigraphic samples: A generalized approach for biostratigraphic data
Maximum likelihood analysis
The probabilistic approach to correlating and dating of isolated paleontological samples by likelihood analysis results in sample age estimates with defined confidence intervals. Thus, all of the uncertainty inherent in age assessment is explicit in the results.
Petrological and geochemical investigations of potential source rocks of the central Congo Basin, Democratic Republic of Congo
Two potential source rocks
Sediments of the Loia and Stanleyville Groups, central Congo Basin, have excellent potential as source rocks. Exploration for conventional oil should focus on areas where the Late Jurassic to Early Cretaceous sequence has reached greater maturity rather than the study area in this paper.
Quantification of static connectivity between deep-water channels and stratigraphically adjacent architectural elements using outcrop analogs
The importance of static connectivity
Margin connectivity and sand-on-sand connectivity are affected by architectural elements, stacking pattern of channel elements, setting on the slope to basin profile (confined, weakly confined, and unconfined), and sand content. Understanding these elements can help constrain reservoir models.
Tectonic geomorphological investigations of antiforms using differential geometry: Permam anticline, northern Iraq
Curvature analysis
A curvature analysis performed on the Permam anticline, northern Iraq, is used to classify the folded surface into geologically relevant shapes. Using the same digital elevation model, geomorphological-oriented studies as well as tectonic-oriented studies are feasible.
Hydrodynamic aquifer or reservoir compartmentalization?
Misunderstanding can be costly
Changes in the oil-water contact depth across a field can imply reservoir compartmentalization or an underlying hydrodynamic aquifer. This study presents a method for making this distinction by estimating the time for a steady state oil-water contact to be established.
Source of molten elemental sulfur and hydrogen sulfide from the Inigok well, northern Alaska
Where did the sulfur come from?
An unusual occurrence of liquid elemental sulfur and hydrogen sulfide (H2S) was found in Inigok #1, an exploratory well drilled south of Prudhoe Bay in 1978. The likely source of the sulfur was the H2S, while the source of the H2S is more problematic and may have been pyrite.
Innovative methods for flow-unit and pore-structure analysis in a tight siltstone and shale gas reservoir
Routine methods not appropriate
A non-routine method for flow unit identification to characterize tight gas reservoirs incorporates profile permeability measurements corrected to in-situ stress conditions and dominant pore size estimates from low-pressure N2 adsorption isotherms.
Origins of gypsum in deep carbonate reservoirs: Implications for hydrocarbon exploration and production
Gypsum can exist below 3500 feet
The presence of gypsum in reservoir rocks can effect porosity calculations. It may form in preference to anhydrite depending on stratigraphic considerations. Its conversion to anhydrite depends on lithostatic pressure, local geothermal gradient, and pore brine fluid availability.
About the BULLETIN
First published in 1917 as the Bulletin of the Southwestern Association of Petroleum Geologists--AAPG’s predecessor organization--in order to disseminate scientific material from annual meetings of the S.A.P.G., the AAPG Bulletin changed its name one year later when S.A.P.G. became AAPG.
The AAPG Bulletin has been delivering quality research to the scientific world ever since. The first issue contained papers written by the best-known geologists of the day, and included papers on such topics as South America, Europe, and general geologic problems of structure and sedimentation.
While the 21st-century AAPG Bulletin has undergone some changes since 1917, enlarging to 8 ½ x 11” size to incorporate more material and being published digitally as well as in print, it continues to adhere to the primary purpose of the organization, which is to advance the science of geology especially as it relates to petroleum, natural gas, other subsurface fluids, and mineral resources.
Delivered digitally or in print monthly to each AAPG Member as a part of membership dues, the AAPG Bulletin is one of the most respected, peer-reviewed technical journals in existence, with recent issues containing papers focused on such topics as the Middle East, channel detection, China, permeability, subseismic fault prediction, the U.S., and Africa.