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.
Deep Pressure in the Lower Tuscaloosa Formation, Louisiana Gulf Coast
Published:January 01, 1994
Repeat formation tester (RFT) pore pressure measurements spanning a depth range of 5500-6060 m in the lower Tuscaloosa Formation (Upper Cretaceous) document a pressure discontinuity of >20 MPa at -5680 m forming a pressure seal in two natural gas fields in the Tuscaloosa trend, Louisiana. In the Morganza field the depth to the top of overpressure varies by less than 30 m across two adjacent fault blocks, though equivalent strata are downthrown by 100 to 120 m. In contrast, the depth to the top of overpressure in the nearby Moore-Sams field rises slightly across the same fault. Therefore, the...