| Title | Numerical Analysis of the Decrease in Injectivity of Wells in the Otake Geothermal Field, Japan |
|---|---|
| Authors | Itoi, R., Fukuda, M., Jinno, K., and Tomita, T. |
| Year | 1987 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | |
| Abstract | Thefield tests of injecting geothermal hot water into two wells have been conducted for 638 t o 656 days in the Otake geothermal field. The permeability-thickness product decreased from 224 t o 0.79 darcy-m for Well and from 91 t o 5 darcy-m for Well R-2. This is probably caused by the decrease in permeability due to the deposition of silica i n cracks around the wells. A mathematical model, which describes the permeability decrease caused by the silica deposition in a porous reservoir, has been used t o analyze the f i e l d data. The rate constants of silica deposition used i n calculation were determined by the laboratory experiments on silica deposition in porous media. A reasonable match was obtained between the measured and the calculated water levels for Well The zone where the permeability decreased significantly was calculated to be in the vicinity o f the well, within 8 m in radius. Outside this area, the decrease i n permeability is negligible 1. |