Geology Reference
In-Depth Information
General conclusions from the studies performed in this chapter are:
1. Analysis and specialized interpretation of the distribution
patterns of paleo- and present-day pore and formation
pressure gradients takes into account various options in
interrelations within the sedimentary sections of compe-
tent and incompetent sequences. This opens radically new
approaches to the identification and objective evaluation of
the environments for the formation, placement, existence,
preservation and dissipation of the regional and local oil and
gas occurrences and their reliable forecast.
2. Environment of regional oil and gas occurrence formation
and preservation usually corresponds with:
t
Small pressure gradients between clays and reservoirs
(moderate relaxation rate of syngenetic AHPP for the
hydrocarbon-generating clay series accompanied by for-
mation pressure increasing to become abnormally high
in the adjacent accumulating reservoirs).
t
Situation of limited possibility for oil and gas accumu-
lation and likelihood of its identification (significant
pressure gradients between the clays with practically
non-relaxable lithostatic level AHPP and reservoirs with
normal formation pressure).
t
Dissipation of hydrocarbon saturation (no pressure gra-
dients and the development hydrostatical environment in
the pore space of clays and contacting reservoirs).
3. The formation and placement of regional and local oil and
gas occurrence is realized as a function of active large-scale
hydrogeological processes defining the likelihood of emigra-
tional release of pore and fracture space in the natural reser-
voirs from earlier fill of syngenetic ground water. Thus, void
volume is generated in them subject to the saturation with
migrating hydrocarbons.
4. Everywhere zones and areas of oil and gas accumulation
are spatially associated with foci and areals of surface and
depth-related, open or dispersed, paleo- or present-day
discharge by geo-fluid-dynamic systems (zones of piezo-
metric minima). The discharge is implemented in inter-
formational and intraformational vertical-horizontal fluid
cross-flows through fault systems, elevated fracturing zones,
diapir plug contacts, mud volcano eruptions, etc.; tectonic,
