Case Studies on High Angle Drilling of Geothermal Wells and Future Prospects at Takigami Field

Abstract

Some geothermal fields can be effectively developed by high angle drilling. This method can minimize the number of drill sites and consequently help minimizing the environmental impact for construction of geothermal power plants. The high angle drilling method which uses MWD and High Torque Down Hole Motor, has become widespread for oil field development in Japan. We have applied the method to drill and complete two wells at Takigami geothermal field in Oita Prefecture. These two wells with maximum hole angles of 61° and 56°, were accurately controlled. One of these wells succeed to turn the hole azimuth 40° while it was keeping the maximum hole angle 56°. By analyzing borehole data while drilling to total depth, it is concluded to be very important to remove cuttings completely to the surface. Moreover, the total well cost of these wells was dramatically cut by shortening the drilling program due to effective utilization of this method and by increasing penetration rates.