Jökull - 01.12.1987, Blaðsíða 20

TABLE 2 DATA ON BOREHOLES IN KRAFLA.
CEMENTED CASINGS -------..... -............ LINER
Well nr Drilled year Depth (m) Diam. n Depth (m) Diam. C) Depth (m) Diam. (”) Depth interval (m)
KW-l 1974 1138 14 79 8% 296 6% 285-1135
KW-2 1974 1204 14 80 8% 298 6% 284-1183
KG-3 1975 1740 i3-y« 114 9% 604 7% 584-1671
KJ-3A 1983 985 13% 336
KJ-3A 1984 9% 302-663
KG-4 1975 2002 13| 114 9% 594
KG-5 1975 1299 13% 114 9% 643
KJ-6 1976 2000 13% 142 9% 576 7% 491-1933
KJ-7 1976 2165 13% 276 9% 808 7% 715-2101
KJ-7 1977 1% 187
KG-8 1976 1658 13 K 142 9% 537 7% 517-1646
KJ-9 1976 1101 13Vs 275 7% 251-1100
KJ-9 1977 1263 9% 1074 7% 1062-1259
KJ-9 1982 1280 7% 1063-1274
KG-10 1976 2082 13% 275 9% 805 7% 775-2060
KJ-11 1976 2217 13% 275 9% 788 7% 754-2194
KJ-11 1978 7% 766-1250 7% 1290-2194
KG-12 1978 2222 13% 283 9% 985 7% 959-2220
KJ-13 1980 2050 13% 284 9% 1064,5 7% 1028-2037
KJ-13 1983 1780 7% 870-1706
KJ-14 1980 2107 13% 210 9% 705 7 1527-2099
KJ-15 1980 2097 13% 295 9% 1093 7 1054-2097
KJ-16 1981 1981 13% 206 9% 669 7 1836-1951
KJ-17 1981 2190 13% 206 9% 692 7% 642-1964
KJ-18 1981 2215 13% 200 9% 669
KJ-19 1982 2150 13% 200 9% 649 7 495-2009
KJ-20 1982 1823 13% 211 9% 646 7 604-1770
KJ-21 1982 1200 13% 286 7 240-1170
KJ-21 1984 9% 273 9% 273-1043
KJ-22 1983 1877 13% 155 9% 565 7 522-1850
KJ-23 1983 1968 13% 190,5 9% 536
Leirbotnar field, which is the largest geothermal field
within the Krafla caldera.
Altogether 24 wells (>1000 m) have been drilled in
the three different well fields in Krafla. The basic design
statistics of the wells are summarized in Table 2. The
typical Krafla well is cased with a 13 3/8” anchor casing to
200-300 m depth and production casing to 600-1100 m
depth. The production part is drilled with an 8 1/2”
drillbit to about 2000 m depth and cased with a 7” slotted
liner.
FIELD CHARACTERISTICS
The production characteristics of the three well fields
at Krafla differ widely as is apparent when simplified
temperature /depth profiles for them are compared (Fig
7). The Leirbotnar field is divided into two distinct
reservoir zones. The upper zone which extends down to
approximately 1 km depth is water saturated with a
mean temperature of 205°C. The temperature of the
lower zone below 1 km depth is in excess of 300°C and
boiling conditions extend below 2 km depth where the
temperature is 350°C. The upper zone vanishes at the
Hveragil gully and to the east in the Suðurhlíðar field a
boiling reservoir extends from the surface down to at
least 2 km depth. In the Hvíthólar field a boiling system
extends from the surface down to 700 m depth but below
18