Geology Reference
In-Depth Information
Peninsula. So, the amount of the effused depth-origins alkaline water may
probably be increased several times, especially in consideration of the mud
volcano activity in this area, which was also accompanied by the release to
the surface of its substantial volume.
The quoted data indicate, therefore, that the hydrocarbon accumula-
tion in structural traps on the Apsheron Peninsula was occurring against
the background of intense Meso-Cenozoic geo-fluid-dynamic system
discharge.
The factual data also establish the following. The patterns in spatial
placement of the hydrocarbon accumulations and predominant oil- and
gas-accumulation zones objectively existing in the South Caspian Basin
are expressed as drastic increase in the Productive Sequence section's gas-
saturation down its regional dip (i.e., as faulting decreases and the insula-
tion of accumulations from the surface improves). These patterns result in
the formation of mostly gas (gas-condensate) accumulations in the sub-
sided zones and mostly oil accumulations in the most uplifted and strongly
faulted zones (Mekhtiyev, Tsaturyants and Rachinsky, 1968). These pat-
terns appear to be controlled and practically defined by the drainage con-
ditions of underground reservoirs.
In areas where geologic environment facilitates intense invasion of the
depth-origin hydrocarbonate-sodium water into the section and emigra-
tion onto the surface of the section-syngenetic chlorine-calcium brines, oil
fields usually group. Basically, under conditions of limited injection and
emigration, zones of dominant gas accumulation form.
Within the South Caspian region, the former spatially correspond with
most faulted external flank framework. It includes the Apsheron Peninsula,
Lower Kura Depression, Balkhan zone of highs and the Apsheron
Archipelago. The latter are less effected by faulting and mud volcanic activ-
ity. Those are the subsided areas of the South Apsheron shelf (the subsided
zone of the Apsheron Archipelago), Gograndag-Chikishlyar zone of the
West Turkmenistan and the central South Caspian.
Based on data from all reviewed basins we described the conjunction
between commercial oil and gas occurrences and the territories, inter-
vals and formation stages of piezometric minimums. The data show that
this conjunction exists in most of actual geologic environments. It does
not depend on the specifics of the general geologic and petroleum geo-
logic attributes and parameters (platform and mobile belt regions, types
of the sections and reservoirs, conditions, attitude and morphology of
the reservoirs, traps, accumulations and fields). It defines, therefore, the
fundamental law:
the location and timing of hydrocarbon accumulat-
ing processes are strictly controlled by the location and timing of the
