Page 277 - Geology and Geochemistry of Oil and Gas

240 MATHEMATICAL MODELING IN PETROLEUM GEOLOGY

The first and second alkalinity exhibit simple correlation with the various
2
components of brine. The first alkalinity depends on the content of SO 4 ion as
follows:
A 1 ¼ c drSO 2 (11.57)
4
where c ¼ 30 and d ¼ 50 for Neft Dashlary Formation waters.
The second alkalinity depends on the content of Ca 2+ and Mg 2+ ions:
2þ
A 2 ¼ erðCa 2þ þ Mg Þ (11.58)
where e ¼ 0:375 for Neft Dashlary Formation waters.

There is also relationship between A 2 and HCO 3 content:
A 2 ¼ frHCO (11.59)
3
where f ¼ 0:085 for formation waters in Daghestan Mesozoic rocks, Eastern Pre-
Caucasus (Russia).

+
Relationships between the first alkalinity or second salinity and rNa /rCl ratio is
very useful. These relationships, however, are non-linear. A more convenient cor-

relation is the linear correlation between A 1 or S 2 and rCl /rNa + ratio:

þ
A 1 ¼ g ð1 rCl =rNa Þ (11.60)
þ

S 2 ¼ g ðrCl =rNa 1Þ (11.61)
where g ¼ 95.
Established analytical and statistical relationships may be expanded in the case
when besides chlorides the formation water also includes sulfates and other salts of

2

strong acids. In this case, r(Cl +SO 4 +NO 3 ) should be substituted for rCl in the
system of Equations 11.45.
The above analytical relationships may be useful for solving various problems
involving formation water hydrochemistry. They also allow inference on the various
formation water characteristics even in the case of the incomplete chemical analysis.
Similarly, the type of formation water and its characteristic coefficients may be
determined from the data on water salinity only. In this case, for example, numerical
values of Palmer’s characteristics may be found from the total water salinity
(Fig. 11.16).
11.2.2.3. Multidimensional models
11.2.2.3.1. Reservoir rocks. Within the Absheron Peninsula and the adjacent South
Caspian offshore areas, clastic rocks of Productive Series are composed mainly of
quartz, feldspar, and various rock fragments. The distribution of rock types in each
formation reflects the cyclic nature of the section. The section is composed of sand-
stones, siltstones, shales, unsorted sediments, and evaporites.
The mineral composition of the Middle Pliocene rocks of the South Caspian Basin
is characterized by several different associations of light and heavy minerals. Min-
erals of the light group include quartz, feldspar, and various rock fragments. Five
heavy mineral groups were identified: (1) ore minerals (pyrite, magnetite, limonite,
leucoxene), (2) stable minerals (garnet, zircon, tourmaline, rutile), (3) kyanite or