Geology Reference
In-Depth Information
t
Waters of unproductive intervals compared to forma-
tion waters of gas-condensate accumulations have higher
salinity, low primary alkalinity, no sulphates and organic
components.
t
Some parts of the Productive Sequence section contain gas-
condensate accumulations and are saturated with hydrocar-
bonate-sodium waters. Primary alkalinity factors usually
do not exceed 23%-equiv., oil accumulations most often
have this attribute on the order of 25%-equiv. and higher.
In waters of unproductive intervals, primary alkalinity is
lower (3-5%-equiv.) and in some cases these intervals are
saturated with hard waters.
t
Waters with maximum primary alkalinity values (40-50%-
equiv.) usually come with oil accumulations.
t
The soluble organic acid salt content in total alkalinity in
waters of gas-condensate accumulations is always higher
than 25%, whereas in oil accumulations it is much lower
(3-10%).
The noted features have regional nature and according to the actual
data are valid also for the Red-Bed Sequence of West Turkmenistan
(Kurbanmuradov, 1963).
The application of the above criteria in the actual geologic conditions
of individual structures is most effective using the comparison technique.
Its substance is this: Compared a hydrochemical sections of a structure
under appraisal and of the closest to it but located up the regional dip
within the same anticlinal zone where commercial oil and gas occur-
rences are established. Let us assume that in the equivalent horizons of
the structure under appraisal, formation water salinity is higher and alka-
linity (
А
) is 1.5-2 times lower (secondary salinity 5-10%-equiv. higher)
than that in the adjacent oil-saturated trap. Then, on condition of elevated
contents of soluble salts of organic acids in waters (greater than 25% of
total alkalinity) and elevated contents of sulphates,there are many reasons
to suggest the presence in the penetrated interval of gas and condensate
aggregations. The primary alkalinity factor values of about 35-45%-equiv.
in the hydrocarbonate-sodium water medium indicate the likelihood of
oil accumulations in this target.
This is the situation with the forecast of the accumulation type within
individual local structures. It is importance to review hydrogeological and
hydrochemical criteria for the identification of regional zones of the pre-
dominant oil and gas accumulation.
