Geostatistical Methods for the Study of Pressure Compartments: A Case Study in the Hilight Oil Field, Powder River Basin, Wyoming
H. P. Heasler, L. Borgman, X. Chen, 1994. "Geostatistical Methods for the Study of Pressure Compartments: A Case Study in the Hilight Oil Field, Powder River Basin, Wyoming", Basin Compartments and Seals, Peter J. Ortoleva
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This chapter introduces the variogram method for analyzing the geometry of pressure compartments. Pressure and hydraulic head data from 192 wells in the Hilight oil field, Powder River basin, Wyoming, were used in this study. Variograms were calculated for various directions. Results indicate that hydraulic head and pressure are spatially correlated, especially in directions parallel to the axes of elongation of compartment cells. The average pressure compartment was estimated via the variogram method to be an ellipse with major and minor axes of 5.3 and 2.7 mi (8.5 and 4.3 km). The major axis trends 15° azimuthally, the minor axis 285°.
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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.