Jökull - 01.12.1987, Page 24

Fig. 12. The alteration zones of the
Leirbotnar and Hvíthólar well fields. —
Mynd 12. Lega ummyndunarbelta i
Leirbotnum og Hvíthólum.
WELL AND RESERVOIR TESTING
All the wells have been carefully logged for temperature
and pressure during and after drilling. Interpretation of
these logs has contributed to the understanding of the
physical properties of the geothermal system. The three
drilling fields have widely different temperature charac-
teristics as mentioned earlier. Fig. 13 shows a thermal
NW to SE section through the Leirbotnar and Suður-
hlíðar fields from well KG-8 to KJ-18. A “cold” tongue
coming in from the north is very prominent in the upper
part of wells KW-2 and KG-10 (Fig. 14). In the Hvíthólar
field the hot fluid does not extend below 700-1000 m
depth and a much cooler regime with a temperature of
180°C at about 1000 m depth increasing to about 250°C at
1900 m, is found below it.
The pressure profiles show that in the drilling fields
the highest pressures in the Suðurhlíðar field suggesting
possible flow from thre to the Leeirbotnar field (Guð-
mundsson, G 1983). There are two pressure maxima,
near wells KJ-17 and KJ-20 respectively suggesting two
different upflows (Fig. 15).
In the Leirbotnar field the pressure decreases to the
south and west, being highest in wells KW-1 and KW-2
and lowest in KJ-6 (Fig. 14). The pressure in the Hvít-
hólar field is similar to that in well KJ-6.
To obtain data on the permeability of the reservoir
and an estimate of well productivity, injection tests have
been carried out at the end of drilling of each well.
(Sigurðsson & Stefánsson 1977 and Sigurðsson 1978)
Few drawdown tests have been conducted, and recently
Fig. 13. Temperature cross section of
the Leirbotnar and Suðurhlíðar well
fields. — Mynd 13. Hitadreifing í Leir-
botnum og Suðurhlíðum.
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