| Abstract |
As part of an informal agreement between Lawrence Berkeley Laboratory (LBL) and four Icelandic institutions responsible for the exploration and development of geothermal energy in Iceland, well data from the Krafla geothermal field in Iceland have been analysed. The data consist of injection test data and production data. The injection test data were analyzed for the reservoir transmissivity and storativity. Analysis of the production data to determine the relative permeability parameters for the Krafla field is in progress. In this paper, the analysis of injection tests at the Krafla field will be described. The Krafla geothermal field is located on the neovolcanic zone in north-eastern Iceland (Figure 1). The neovolcanic zone is characterized by fissureswarms and central volcanoes. The Krafla geothermal field is located in a caldera (8 x 10 km), with a large central volcano, also named Krafla. XBL 793-6332 Surface geophysical exploration at Krafla was initiated in 1970. In 1974, two exploration wells were drilled, and the subsurface data indicated the presence of a high temperature (>3OO0C) geothermal field. Presently, 18 wells have been drilled at Krafla: the locations of the wells are shown in Figure 2. Stefansson (1981) has presented a detailed description of the reservoir system at Krafla; his model is summarized below. In the old well field ( wells 1-13, & 15) pressure and temperature data from the wells have indicated the presence of two reservoirs. The upper reservoir contains single phase liquid water at a mean temperature of 205OC. This reservoir extends from a depth of 200 m to a depth of about 1100 m. The deeper reservoir is two-phase, with temperatures and pressures following the saturation curve with depth. This reservoir directly underlies a thin confining layer at a depth of 1100-1300 m and it extends to depths greater than 2200 ~n ( the depth of the deepest well ). The two reservoirs seem to be connected near the gully, Hveragil. In the new well field (south of M t. Krafla, wells 14, 16-18), the upper reservoir has not been identified, and only the two-phase liquid dominated reservoir seems to be present. |