Page 228 - Geochemistry of Oil Field Waters

COMPOSITION OF OILFIELD WATERS 21 5

TABLE 7.VIII
Pennsylvanian system - highest concentration of a constituent found, average concentra-
tion, and number of samples analyzed
Constituent Concentration (mg/l) Number of samples
highest average

Lithium 35 7 45
Sodium 101,000 43,000 951
Potassium 710 170 57
Rubidium 2.30 0.55 25
Cesium 8.50 0.15 19
Calcium 205,000 9,100 9 50
Magnesium 15,000 1,900 947
Strontium 4,500 600 70
Barium 640 30 41
Boron 70 15 54
Manganese 105 60 2
Chloride 270,000 87,600 950
Bromide 3,900 490 57
Iodide 1,410 210 52
Bicarbonate 1,200 130 897
Carbonate 70 40 2
Sulfate 5,400 430 7 56
Organic acid
as acetic 2,300 430 44
Ammonium 3,300 300 51

Table 7.V indicates that oilfield water samples taken from Cretaceous age
strata were enriched in lithium with respect to sea-water. The highest lithium
concentration found in 26 samples was 13 mg/l.
Table 7.VI indicates that oilfield waters taken from Jurassic age strata
contain up to 400 mg/l of lithium, which, compared with sea water (Table
7.1), represents a concentration factor of 2,000. Compared to the hydro-
lyzates in sedimentary rocks (Table 7.11), the concentration factor is about
9.
The lithium concentration in oilfield waters taken from Permian age strata
averaged 3 mg/l (Table 7.VII). Only three samples were available for use in
determining this average.
Table 7.VIII indicates that the lithium concentration averaged 7 mg/l in
45 samples taken from Pennsylvanian age strata. This represents a concen-
tration factor of 35 compared with sea water (Table 7.1).
Table 7.IX indicates that the lithium concentration in oilfield waters
taken from Mississippian age strata is enriched by a factor of 45 compared
with sea water. Table 7.X indicates a similar enrichment factor of 250 for
oilfield waters taken from Devonian age strata. For waters from Silurian age
strata (Table 7.XI) the enrichment factor found was 185; for the Ordovician