Geology Reference
In-Depth Information
Geobaric Field in Alpine
Mobile Belt Basins
An important feature in the mobile belt basins is the presence in the sec-
tion of intervals with abnormally high (super-hydrostatic) pore (AHPP)
and formation (AHFP) pressures
1
. he zones where these pressures occur
are associated with various stratigraphic units. Their intensity varies in the
1
Here and thereafter the term “abnormally high” is used for a pressure exceeding
the hydrostatic pressure (i.e., the pressure from a column of liquid with density
1,000 kg/m
3
and with height from formation depth to the surface) by 15÷20 %.
The numeric values of the pressure abnormality parameters are computed using
its excess (
ΔР
=
Р
measured
- Р
app.hydrostatic
) and the abnormality factor. The abnormality
factor is the ratio of measured pressure and the apparent hydrostatic pressure at the
same depth (
K
AHFP, AHPP
=
Р
measured
/
Р
app.hydrostatic
). The differences in density between
oil, gas and formation water cause the occurrence of “excess” super-hydrostatic
pressure and affect the results. For this reason, the measured formation pressures
in oil and gas accumulations are normalized for the corresponding contact sur-
faces with the edge water (OWC, GWC). I.e., our analysis takes into account only
those data appropriate for the baric environment within the hydrodynamic system
outside the outline of productive reservoirs.
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