Faculty of Engineering UGM held a public lecture entitled "How to Minimize Drilling Risk, Wednesday (19/10) in the Auditorium of the Faculty. On this occasion, the Faculty invited President and Manager of Reservoir Engineering Services, GeothermEx, Inc., California - USA, Dr. Subir K. Sanyal as speaker.
On the occasion, Subir mentioned almost more than 70% of lands in Indonesia are known to have geothermal resource base of more than 50 MW and nearly half (40) have resource base of approximately 100 MW. Commercial wells vary in capacity from 3 MW to more than 40 MW with an average value of 9 MW.
"The mean, median, and maximum productivity of geothermal resources in Indonesia are much larger compared to those in most other countries. We estimated the most possible range of productivity from the productivity of drilled wells in the whole world only reaches 4-6 MW," Subir said.
According to Subir, besides having land with large geothermal resource base, Indonesia also has a large geothermal capacity. Meanwhile, the cost of drilling a well is much smaller compared to other countries. "Therefore, the overall risk of existing resources in geothermal project in Indonesia should also be lower than that of other countries," he explained.
Further about the success rate in drilling, Subir said that a drilling’s success in average increases along with the increasing number of wells that are drilled. This is because of an increase in sample size and learning curve effect. In general a drilling’s success rates ranges from 50-90%, with a more typical range of 60-70% with an average of about 67%.
"For Indonesia itself, the drilling success rate reaches 63% as well as in most other countries," Subir said.
Meanwhile, Subir said that the occurrence of drilling failure is more due to mechanical problems during the drilling. In addition, it is also due to low pressure in the reservoir, the reservoir is narrow, and a number of other issues that are on the surface of the well being drilled. "Inappropriate temperature also becomes one of the causes of this failure," he added.