Customizing Drilling Engineering in Geothermal Drilling Campaign, by Utilizing Standard-Temperature-Rated Tools and Achieving High Operating Efficiency, a Case from Indonesia Major Geothermal Field Dieng-Patuha

ABSTRACT Geothermal resources in Indonesia are a growing component of the country's renewable energy landscape. Geothermal drilling operations has been considered as high complexity. The harsh drilling environment is characterized by hard formations, high temperatures, and lost circulation that presents significant obstacles that need to be addressed for smooth drilling operations. The common solution is the utilization of high-temperature-rated tools in the downhole drilling BHA (bottom-hole-assembly). However, this approach can be cost-prohibitive for some projects. This paper will elaborate an alternative solution applied in one of Indonesia's major Geothermal Field campaigns, of deploying standard-rated temperature tools during the execution stage, supported with meticulous planning in the prejob stage. The first step of drilling a directional Geothermal Well with Standard-rated tools requires optimization in trajectory design. Planning a well trajectory that finishes the directional work at interval depth in which standard-rated tool can still survive is the mandatory foundation. Once the temperature increases closer to the standard-tool limit, the next step is to change to rotary BHA and drill the remaining depth. Designing a rotary BHA that can hold the trajectory inside subsurface target radius had its own obstacles. Utilizing software to design the BHA, combined with an offset wells study, has become a powerful tool to deliver an optimized rotary BHA that can drill without deviating too much from the planned trajectory and still hit the target. Optimizing trajectory by limiting maximum inclination and DLS has also improved the drilling performance and hole cleaning from the common lost circulation environment that happens during drilling. Good repeatability of drilling practices during total lost circulation in the subject field of this Paper was important to reduce risk of stuck pipe. Each approach has contributed to the success of the entire campaign: trajectory design that considered faults and lost zones; executing High Temperature intervals to be drilled with standard equipment, including rotary BHA; tool selection and screening that contributed to not having any tool failure; BHA modeling and tendency calibration; utilization of MWD electromagnetic communication instead mud pulsing to mitigate pulsing challenges with aerated mud system in relation to lost circulation; and a simple BHA and trajectory design with fit for purpose concept. All customization from planning up to execution had proven a continuous improvement in the subject fields. As a result, the drilling plan was executed for a total of 22 Geothermal wells, drilling more than 161,000ft with 12,900hrs below rotary table and high operating efficiency utilizing standard rated equipment. This drilling approach proved to be effective, giving the option of lower cost execution to the operators when drilling in Geothermal fields that frequently have challenges. The design and the approach can be extended to other Geothermal projects around the world.