Geology Reference
In-Depth Information
Another school adheres to mostly secondary, allochtonous nature of the
Middle Pliocene hydrocarbon accumulations [Productive Series (PS) in the
western and southern parts of the basin and the Red-Bed Series (RBS), in
the east]. These scientists believe that most hydrocarbons migrated into PS/
RBS from deep Paleogene-Miocene and Mesozoic deposits through frac-
tures, faults, contacts of piercing diapirs, mud volcanoes, etc. The process
has been a component of the dominant mechanism of large-scale repetitive
intraformational stepwise vertical fluid cross-flow at times of increased tec-
tonic activity. Proponents of this view, however, do not reject a possibility
that some hydrocarbons in some portions of the basin could have been gen-
erated in the PS/RBS, but their volume is not considered significant.
To support their position, both groups use the same data. They include
bitumen study results, patterns in spatial distribution of fields, dispersed
organic matter (DOM) and hydrocarbon contents in the surrounding rocks.
All of these items allow non-unique interpretation. Therefore, the objec-
tive of further research is to identify and study processes, mechanisms and
phenomena that can be uniquely interpreted within a reasonable range of
confidence.
We believe that the preference should be accorded to the quantitative
evaluation of chronological, stratigraphic, depth-related and tempera-
ture-related ranges of hydrocarbon generation potential in the sedimen-
tary section. This evaluation should be based on a number of factors. They
include:
1. Integral consideration of the stage-wise transformation of
dispersed organic matter as a function of source material.
2. Duration of transformation process.
3. Rate of deposition.
4. Lithophysical composition of individual source-rock
intervals.
5. Outflow rate of liquid and gaseous products.
6. Space/time dynamics of geotemperature.
7. Baric environment and the tectonic movement direction.
8. Real existence of the temperature-differentiated zones and
phases (“windows” and stages) of oil-, gas-, condensate- and
late-catagenic (deep) methane-generation.
9. Generation of “dry” and “sour” gases (CO
2
, N
2
, etc.).
Before discussing the above issues, it is beneficial to outline the region's
geology. The South Caspian Basin is a typical Alpine intermontane depres-
sion overlying a heterogeneous Jurassic substrate. The sediment cover,
