| Title | Laboratory Tests on the Drillability of Rocks and Evaluation of Tri-Cone Bits at Elevated Temperature |
|---|---|
| Authors | Misawa, S., Karasawa, H., Morita, K., Hayamizu, H. |
| Year | 1982 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | |
| Abstract | The air drilling test facility was manufactured to investigate the drillability of rocks and the life-time of full-scale rock bits at elevated temperature; Bits used for these tests are 9 tungsten carbide inserts tri-cone bits of diameter. The results obtained from the drilling tests for granite and andesite up to 350?C showed that the penetration rate for granite increased with a rise of rock temperature, but there was no significant change of penetration rate for andesite. time tests of 7 bits with h o t cast-iron blocks conducted to evaluate the bit performance at elevated temperature. Through the tests. bi t s were encountered several troubles such as loosing or breakage of tungsten carbide inserts and damage of rotation mechanism of the roller cutter caused by breakage of the bearing, deterioration the seal and entering of cast-iron cuttings into the bearing. Practical experience and knowledge given from the tests will be useful to point out disadvantageous portions of conventional tri-cone bits under high temperature and for further improvements of the bit. |