Geology Reference
In-Depth Information
5.2.1.4
The Irrawaddy-Andaman Depression
The region is dominated by vertical fluid migration from the lower to the
upper stages of the sedimentary section with limited role of other water-
exchange mechanisms. This is caused by factors such as:
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Strong facies variability causing a lens-shaped nature of
reservoirs.
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Severe shale-out toward the center of the depression.
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Consistent pinch-out toward its flanks of the lower compo-
nents of the sediment section resulting in the formation of
hydraulic “dead ends”.
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Genetic association of local folding with the fault tectonics.
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Exceptionally intense faulting of individual structures and
anticlinal belts.
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Hydrodynamic separation by regional faults of the depres-
sion's flank zones from its subsided central portion.
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Neotectonic activity in the region.
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Common mud volcanism joining large stratigraphic and
physical ranges.
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Numerous surface oil-, gas- and water-shows around deep
fault zones.
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Clear control of oil and gas occurrences by faults (Rachinsky,
1987, 1989).
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Geochemical affinity of all oils in the sedimentary sequence
(Anikeyev, Bronovitsky and Taliyev, 1985; Oil and gas of
the foreign fields. Reference book, 1977; Collins, 1975;
International Petroleum Encyclopedia, 1976).
5.2.1.5
The Los Angeles Basin
The type of infiltration fresh water manifestations in the section and over
the area of the region is evidence against the current existence there of an
artesian type waterhead system. These manifestations are:
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Their localization only on individual denuded structures
and only in the exposed head portions of the Pliocene and
Pleistocene beds.
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Insignificant coverage by these manifestations of field sec-
tions (to a depth of about 200-300 m).
The main general hydrogeological factors limiting such a water-
exchange system are:
