A study of the application of turbine coring drilling technology to hot dry rock drilling

Exploration of hot dry rock in China has just started. In order to accurately evaluate the amount of hot dry rock geothermal resources in China, high-quality hot dry rock drilling cores are needed. However, there are few researches on coring drilling of hot dry rock under the conditions of high temperature, high hardness and high grinding, which seriously restricts the accurate evaluation of hot dry rock geothermal resources. Therefore, independent research and development of the turbodrill Φ127 mm are carried out. The HDR-1 well in Zhangzhou of Fujian and the GR1 well in Gonghe of Qinghai were drilled and the research and application of hot dry rock drilling coring were performed to verify the research and development of turbodrill and the suitability of the KT-140 coring drilling tools and the matching of turbodrill and diamond core bit. The high temperature and hard rock characteristics of turbodrill working under the well conditions are revealed, the test of high temperature of 236 ℃ at the bottom of the bore is withstood, and the application test of turbodrill parameters is obtained. Compared with the conventional coring drilling technology, the turbodrill composite coring drilling technology not only plays an important role in the performance of high rotating speed of the turbodrill, but also makes full use of the characteristics of high temperature resistance, grinding resistance, high ground stress resistance, long service life and low on-site labor intensity, which greatly improves the drilling speed of hot dry rock. The method is of high temperature deep hole hot dry rock underground rotary drill driving core bit coring drilling and is the first successful attempt for hot dry rock of turbodrill coring drilling technology. The field test and application may provide valuable construction experience. The results will also provide a new technical support for hot dry rock scientific drilling and deep geothermal resource exploration in China.