| Title | Rock Fracture Mechanics for Design and Control of Geothermal Reservoir |
|---|---|
| Authors | Takanohashi, H., Niitsuma, H. and Takahashi, H. |
| Year | 1988 |
| Conference | Japan International Geothermal Symposium |
| Keywords | |
| Abstract | It has become evident that the productivity of natural geothermal systems is highly dependent upon the existence of fractures and high temperatures in deeper rocks (1). Fracture mechanics studies of the subsurface fracture behavior of rock masses (2)(3) have revealed a decrease in fracture toughness in .high-temperature pressurized hot water environments. The results obtained indicate that subsurface cracks are always active and an abrupt change of well bore pressure including hydraulic fracturing and build-up tests in hot water dominated reservoirs causes fracture extensions in the vicinity of fractures resluting in the generation of acoustic emissions. The acoustic emission technique is utilized to map subsurface fractures and to evaluate their shape, size and orientation in geothermal reservoirs and other geological structures (4). The·technique is also used as a powerful tool for mapping hydraulically induced fractures in hydraulic fracturing as well as for stimulations to improve productivity and the prediction of lost circulation during drilling. Moreover, it is very important to monitor subsurface fracture behavior for the stable and efficient operation of geothermal power plants. This paper describes first of all some results of the AE measurements in the Kakkonda geothermal field, Iwate Prefecture, Japan. In conclusion, the application of the AE technique in the evaluation of geothermal reservoirs based on rock fracture mechanics, extremely useful in geothermal energy development, is described. |