Rit (Vísindafélag Íslendinga) - 01.06.1976, Side 146

15. 9.2 Svartsengi and Reykjanes.
The geology, drilling exploration and chemical composition of the
water in the Reykjanes area are described in detail by Björnsson
(1971). Regarding the Svartsengi area, however, there exist no such
publications at present. Information on the depth of the wells in
Svartsengi and their water temperature were obtained as personal
communications from the staff of the National Energy Authority.
For location of the thermal areas see Figs. 31 and 36.
Deuterium measurements have been carried out on samples col-
lected from two wells in the Svartsengi area (samples No. 80 and
81) and five wells and one hot spring in the Reykjanes area (sam-
ples No. 82-87). For exact location of the wells in the Reykjanes
area see Bjömsson (1971). The ðo-results are summarized in Table
12, together with the Na+ and Cl“ content and the water tempera-
ture. When necessary, the deuterium data in Table 12 have been
corrected for evaporational enrichment.
The water from a depth of 20 m in well H-5 in the Reykjanes
area approximately 200 m west of the central geothermal area has
a ðD = — 31.3%0 and Cl“ = 6230 mg/1. The water temperature is
11°C. Consequently this water appears to be fresh water derived
from local precipitation but to some extent mixed with sea water
which penetrates the uppermost layers of the peninsula. The deu-
terium content of the rain water has not been measured in the
vicinity of this area, but if we assume it to be approximately ðD —
— 48 %0, which is the highest value measured in fresh water on the
peninsula, it tums out that about 34% of the water at a depth of
20 m in H-5 is sea water. Similar calculations by using Cl“ data
give 33% sea water. Below this “fresh” water in H—5 there is pure
ocean water which is still cold. Such water was collected at a depth
of 112 m in H—5 and gave ðD = — 8.8%0. The temperature is 11°C.
All thermal water samples collected in this area gave ðD-values
ranging fram ðD= —17.4%0 (water collected from an open hot spring
in the central geothermal area and corrected for evaporational loss)
to ðD = — 25%0 (water from the drill hole H—1). The mean ðD =
— 21.3%0 is nearly the same as that obtained for the water from the
hole H-8. H-8 is the deepest well in the area and it is cased down
to 300 m and a perforated liner excludes all aquifers above 1000 m.
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