Basin Compartments and Seals
Basins worldwide exhibit an unexpected degree of hydrologic segregation. There can be regions of a sedimentary basin that are isolated from their surroundings by a relatively thin envelope of low-permeability rock with an interior of sufficiently high permeability to maintain a consistent internal hydrostatic fluid pressure gradient. These have been named pressure compartments. Presure compartments have several remarkable features, just one of which is that internal fluid pressures can greatly exceed or be significantly less than any regional topographically controlled hydrologic head or drain. This publication contains 30 chapters that take detailed looks at pressure compartments in general, and detail case studies of these compartments in specific basins, such as the Anadarko and Gulf of Mexico. The volume also looks at other considerations in sedimentary basins such as hydrodynamic and thermal characteristics, and mechanical properties of rock.
Pressure Seals—Interactions with Organic Matter, Experimental Observations, and Relation to a “Hydrocarbon Plugging” Hypothesis for Pressure Seal Formation
Published:January 01, 1994
Jean K. Whelan, Lorraine Buxton Eglinton, Lawrence M. Cathles III, 1994. "Pressure Seals—Interactions with Organic Matter, Experimental Observations, and Relation to a “Hydrocarbon Plugging” Hypothesis for Pressure Seal Formation", Basin Compartments and Seals, Peter J. Ortoleva
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Organic geochemical characteristics diagnostic of pressure seals have been determined for two wells in the Moore-Sams field of the Tuscaloosa trend, Louisiana Gulf Coast (Mix and Bizette wells) and one well penetrating a much weaker pressure transition zone of the Anadarko basin, Oklahoma (Weaver well). Preliminary data suggest these characteristics of organic matter in zones of pressure seals: a rapid increase in vitrinite reflectance near the top of the pressure seal; fractionation of bitumens through the pressure seal with a gradual change from lighter to heavier n-alkanes with increasing depth in the pressure seal; a buildup of hydrocarbons just...