Neville A. Hallam¹, Richard E. Swarbrick¹, Derek Teasdale¹
(1) University of Durham, Durham, England

Abstract: Geological pressure depth plots to identify seals and pressure compartments

Combining geological information in the display of pressure vs depth plots provides a low-cost solution to determination of both lateral and vertical seals in overpressured basin sediments, and the identification of pressure compartments. Single well plots are used to analyse the relationship between pressure transition zones and lithology. Input for the lithology comes from wireline and cuttings data with the highest level of detail required where direct pressure measurements are available. The plots allow identification of pore fluids and hydrocarbon-water contacts as well as vertical "seals" currently acting as pressure transition zones. Multi-well plots do not simultaneously display geology, but permit recognition of pressure compartments in the subsurface. Wells which share the same magnitude of overpressure at the same stratigraphic level are likely to be located in a shared pressure compartment. Multi-well plots can be combined with 2-D and 3-D basin modelling profiles to assess the contribution of lateral transfer to pressure distribution in connected reservoir units. This type of plot therefore challenges the geoscientist to explore for the lateral and vertical seal boundaries, using available structural and sedimentological data. Examples from the Gulf of Mexico, North Sea and S.E. Asia will be used to illustrate the power of pressure depth plots to comprehend the geological environment.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana