Geology Reference
In-Depth Information
t
Within local highs, the positioning of minimal gradients
over the structural crests and their increase on the flanks
and plunges facing the depression areas of the territory.
When prevailing fluid-mass transfer is vertical, the contact area between
migrants and the enclosing geologic medium in restricted by the cross-
section of conducting faults, zones of elevated fracturing, mud volcano
eruptions, hydrogeological “windows”, etc. The baric exchange between
them occurs within a much smaller volume. The flow of high-pressure fluids
from the generation intervals to the accumulation areas occurs at a much
higher rate and through a shorter path (in general cases). The combination
of these moments eventually results in the injection of high-pressure fluids
into the zones of lowered (but normal for a given interval of the section)
pressure and emergence of positive hydrodynamic anomalies. Under this
model, the normalized formation pressure gradient distribution over the
area of the regions should be mosaic and subject to the extent of faulting in
individual areas. The normalized pressure gradient distribution in
hydro-
dynamically opened (to the surface) systems-reservoirs should be their
decrease from the bottom upward in the local structure sections and from
the crestal, most faulted areas toward periphery of the folds. Normalized
pressure gradients in hydrodynamically closed systems (reservoir bed
overlain by a seal) should be maximal at the top of the interval with AHFP.
Downward, toward the source of high-pressure fluids, they should decline.
We will now review the actual patterns in the formation pressure and
spatial distribution of its gradient in major water complexes of the Alpine
regions with active current natural fluid migration. We will approach it
from the position of similarity with the described theoretical models
(Table 5.7, Figures 3.1-3.7, 3.9-3.12).
Lateral ground water flow in the Alpine mobile belt regions sedimentary
sections is limited. The dominant role in their water-exchange belongs to
vertical intra- and interformational cross-flow through various disruptions
in rock integrity. That is supported by the Table data and by analysis in the
previous sections of the lithofacies, tectonic and hydrodynamic factors.
Hydraulic connection between the upper stages and the underlying sec-
tion intervals appears to be closest to the actual situation. This idea is sup-
ported by the following:
t
The aforementioned predominant association between
AHFP and faulted structural traps and drastic decline in
their intensity toward slightly faulted inter-structural zones.
t
The substantial excess of formation pressure in the crestal
zones of accumulations over the excess pressure caused by
