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Direct field observations also objectively confirm the significantly
restricted lateral ground water mobility in fractured carbonate reservoirs
of Asmari and Bangestan formations. These observations show that in
most Zagros trough fields during three years of the oil production shut-in
(1951-1953) not only did the formation pressure not restore to the ini-
tial level but also did not exceed the current formation pressure before
production stoppage. Moreover, OWCs were practically constant despite
significant pressure gradients between the accumulation of aquifer zones
(approximately 15-20 MPa: Graham, Hetherington and Auld, 1956). Low
activity of the aquifer water may be the cause of the fact that almost all
accumulations in the region are being produced under the mixed gas-cap
and solution gas drive without any noticeable advance of the OWC (Aliyev
and Zabanbark, 1974; Hall and Worman, 1973).
Actual data together with the aforementioned considerations objec-
tively assert the domination in the region of large-scale through-pass inter-
formational fluid-mass transfer from the bottom upward. This is supported
by the following factors:
t Present-day vertical and lateral hydrochemical zoning
formed by the cross-flow-injection mechanism (Chapter 2).
t Spatial coincidence between positive ground water salinity
anomalies and elevated fracturing zones in carbonate reser-
voirs and the faulting areas over the tops of local structures.
t Single OWC's in the accumulations of the Asmari and
Bangestan formations (Aliyev and Zabanbark, 1974; Bakirov,
Varentsov and Bakirov, 1970).
t Copious surface oil-, gas- and water-shows over the pro-
ductive structures (Baturin, 1945; Levorsen, 1970; Russell,
1958).
The dominant role of vertical fluid migration in the Zagros trough is
also clearly established by a complex of petroleum geology factors. The
most important of them are:
t All oils in the Mesozoic-Miocene stratigraphic range match
the filtrated type: they are geochemically similar and genet-
ically close (Aliyev and Zabanbark, 1974; Kalinin et  al .,
1977; Hunt, 1982; Joung, Monaghan and Schweisberger,
1977).
t Spotted coloration with heavy oil (migration tracks) in a
number of productive traps in the elevated fracturing zones
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