Skempton’s poroelastic relaxation: The mechanism that accounts for the distribution of pore pressure and exhumation-related fractures in black shale of the Appalachian Basin

AAPG Bulletin ◽  
2021 ◽  
Vol 105 (4) ◽  
pp. 669-694
Author(s):  
Terry Engelder ◽  
Rose-Anna Behr
Keyword(s):  
Pore Pressure ◽  
Black Shale ◽  
Appalachian Basin

Sonic properties as a signature of overpressure in the Marcellus gas shale of the Appalachian Basin

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. D235-D249 ◽  
Author(s):  
Yaneng Zhou ◽  
Saeid Nikoosokhan ◽  
Terry Engelder
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Gamma Ray ◽  
Confining Pressure ◽  
Appalachian Basin ◽  
Burial Depth ◽  
Regression Analyses ◽  
Gas Shale ◽  
Stress Coefficient ◽  
Heterogeneous Rock

The Marcellus Formation, a Devonian gas shale in the Appalachian Basin, is a heterogeneous rock as the result of a complex depositional, diagenetic, and deformational history. Although it is overpressured over a large portion of its economic area, the origin and distribution of pore pressure within the gas shale are not well-understood. We have used the sonic properties of the Marcellus and statistical analyses to tackle this problem. The sonic data come from a suite of 53 wells including a calibration well in the Appalachian Basin. We first analyze the influence of various extrinsic and intrinsic parameters on sonic velocities with univariate regression analyses. The sonic velocities of the Marcellus in the calibration well generally decrease with an increase in gamma-ray american petroleum institute (API) and increase with density and effective stress. Basin-wide median sonic velocities generally decrease with an increase in median gamma-ray API and pore pressure and increase with burial depth (equivalent confining stress), effective stress, and median density. Abnormal pore pressure is verified by a stronger correlation between the median sonic properties and effective stress using an effective stress coefficient of approximately 0.7 relative to the correlation between the median sonic properties and depth. The relatively small effective stress coefficient may be related to the fact that natural gas, a “soft” fluid, is responsible for a basin-wide overpressure of the Marcellus. Following the univariate regression analyses, we adopt a multiple linear regression model to predict the median sonic velocities in the Marcellus based on median gamma-ray intensity, median density, thickness of the Marcellus, confining pressure, and an inferred pore pressure. Finally, we predict the pore pressure in the Marcellus based on median sonic velocities, median gamma-ray intensity, median density, thickness of the Marcellus, and confining pressure.

Description and paleoecology of a population ofAnthraconaiafrom the Pennsylvanian of southern Indiana

1989 ◽  
Vol 63 (4) ◽  
pp. 449-453
Author(s):  
Daniel D. Petzold
Keyword(s):  
Organic Carbon ◽  
Energy Level ◽  
Black Shale ◽  
Significant Variation ◽  
Energy Levels ◽  
Appalachian Basin ◽  
The Other ◽  
Stratigraphic Sequence ◽  
Depositional History ◽  
History Of

Anthraconaiasp. occurs in the thin nonmarine interval that lies between the Upper Millersburg Coal Member and the Lower Millersburg Coal Member (Pennsylvanian, Desmoinesian) in Warrick County, Indiana. Specimens ofAnthraconaiasp. resembleAnthraconaiathat occur in Pennsylvanian and Permian rocks of the Appalachian Basin, but they differ slightly in size, form ratios, or both. Specimens were found in massive, nonfissile gray mudstone; buff-colored, laminated limestone (ostracodal biomicrite, wackestone); and platy black shale. The only statistically significant variation between shells from these different lithologies is that shells recovered from the limestone tend to be more ovate than shells from the other two lithologies. This contradicts the findings of previous investigations in which more ovateAnthraconaiawere found in the more organic-rich sediments of a given stratigraphic sequence. This difference is probably caused by the lack of discernible change in energy level through the depositional history of the interval and suggests that changing energy levels may be more important to the control of the morphology ofAnthraconaiathan the level of organic carbon in the sediment.

Black shale deposition and faunal overturn in the Devonian Appalachian Basin: Clastic starvation, seasonal water-column mixing, and efficient biolimiting nutrient recycling

2000 ◽  
Vol 15 (3) ◽  
pp. 280-291 ◽  
Author(s):  
Adam E. Murphy ◽  
Bradley B. Sageman ◽  
David J. Hollander ◽  
Timothy W. Lyons ◽  
Carlton E. Brett
Keyword(s):  
Water Column ◽  
Black Shale ◽  
Nutrient Recycling ◽  
Appalachian Basin ◽  
Water Column Mixing
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