Jökull


Jökull - 01.12.1987, Page 19

Jökull - 01.12.1987, Page 19
Leirbotnar became contaminated with magmatic gases causing deposition and corrosion in wells with a concom- itant decline in their productivity. Extensive studies of the chemistry of fumarole steam in the area performed in 1978 and 1979 resulted in the definition of three major upflow zones in the Krafla caldera (Gíslason et al. 1978, Armannsson & Hauksson 1980). The Leirbotnar and Leirhnjúkur upflows were found to be contaminated by magmatic gas, but the Suðurhlíðar upflow in the south- ern flanks of Mt Krafla unaffected. In 1980, drilling continued with two production wells in the Leirbotnar field and one exploration well in Suðurhlíðar. The ex- ploration well showed that the reservoir in Suðurhlíðar was not affected by the magmatic activity. This was in an agreement with the fumarole studies. Five wells were drilled in the Suðurhlíðar field in 1981 and 1982. These draw sufficient steam for the production of 15 MWe. As reservoir modeling studies suggest this to be close to the maximum capacity of the field drilling was stopped in Suðurhlíðar. In June 1980 a small field of surface alter- ation near the southern rim of the caldera, the Hvíthólar field, was observed steaming. Chemical analysis of the 85.07. 0884 Fig. 6. Gas concentrations of fumarole fluids in the Krafla geothermal area. 1979-1986 (adapted from Ár- mannsson and Benjamínsson 1986). — Mynd 6. Gas- breytingar í gufuaugum á árunum 1979-1986. Fig. 7. Typical temperature profiles for the three well fields at Krafla. — Mynd 7. Einkennandi hitaferlar fyrir borsvæði Kröfluvirkjunar. steam revealed that a reservoir temperature of 260- 270°C could be expected and that the fluids were not contaminated by magmatic gases. In 1982 and 1983 three wells were drilled in this field one of which is a good producer. The Hvíthólar field is however small and of limited producing capacity. The future drilling strategy in Krafla is yet to be decided. Additional fields could still be found and uti- lized. However the results of studies of well fluids and fumarole steam have shown a large decline in the mag- matic gas component of the reservoir fluids in the affect- ed fields as Fig. 6 shows (Benjamínsson, 1985; Ármanns- son & and Benjamínsson 1986). So the most interesting prospect in the near future is apparently drilling in the 17
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