Geology Reference
In-Depth Information
significant depth interval of up to 14 km, providing the fol-
lowing preconditions are met:
1. Mostly subsiding tectonic regime during Mesozoic
through Quaternary over the most of the South-Caspian
Basin.
2. Relatively high depositional rate.
3. Specific lithophysical composition of the sediment cover
(the presence of thick hydrocarbon-generating, accumu-
lating and sealing sequences).
4. Significant faulting that provides for hydrodynamic com-
munications between the oil and gas generation nodes
and accumulation traps (a necessary precondition of the
commercial oil and gas occurrences).
5. High density of local structures.
6. Intense mud volcanism facilitating significant fluid
cross-flow from one formation to the next.
The Paleogene-Miocene structural-formational
sequence at the current phase of geological evolution
is the major generation zone of liquid hydrocarbons in
the region. It feeds the overlying and, in part, underlying
(Upper Cretaceous) natural reservoirs.
B. The following facts attest to a low probability of the ini-
tial PS/RBS reserves/resources potential being 17 BT of oil
equivalent (Rachinsky
et al
., 2007) as a result of internal
hydrocarbon generation capacity:
1. Spatial distribution of hydrocarbon accumulations in
the Middle-Pliocene PS/RBS, which is the main oil-
and gas-accumulating complex in the South-Caspian
Basin.
2. Continuous increase in the gas saturation of the section
down the dip of regional folded systems accompanied
by the replacement of oil and oil-gas accumulations by
gas-oil, oil-gas-condensate, gas-condensate-oil and gas-
condensate accumulations.
3. Increase in the section's total gas saturation with the
stratigraphic and hypsometric depth.
4. The association of oil accumulations with tectonically
deformed, commonly eroded (denuded) structural traps
often affected by mud volcanism, and association of gas
(gas-condensate) accumulations with unfaulted local
highs.
