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