Presented: Geothermal Rising Conference 2025 – Matthew White, John Clegg, Steve Krase and Rochelle Longval, Hephae Energy Technology.
Read Published Paper.
ABSTRACT
A paper presented by the authors at GRC in 2024 (GRC Transactions, Vol. 48) described the need for high-temperature drilling equipment to enable the accurate drilling of deep, hot EGS (Enhanced Geothermal System) and AGS (Advanced Geothermal System) wells (Clegg et al., 2024).
It noted that although the oil and gas industry has made great strides in getting the operating temperature of downhole electronics from 120°C to 175°C, and, even on rare occasions, to 200°C, the approaches taken in oil and gas tools do not lend themselves to getting to the even higher temperatures that unconventional geothermal will need. Accordingly, it described a unique, blank sheet of paper, approach to the design and packaging of electronics and sensors, to create a brand-new tool that combines the functions of Measurement While Drilling (MWD) and Rotary Steerable Systems (RSS) and which is intended to break that 200°C barrier.
A year on, the authors are able to show in detail a comprehensive test plan that was designed to test all the sensing and electronic assemblies required for such a system under conditions which simulated the harsh conditions likely to be seen in geothermal wells. The test program included long-term operation at temperatures up to 230°C (446°F), with all electronic functions being exercised. It also included a high temperature operation (again up to 230°C) simultaneous with high levels of vibration. The vibration levels were selected to be higher than those normally used to qualify oil and gas tools because shock and vibration are expected to be even higher in the hard, high friction basement formations that EGS and AGS will most likely inhabit than in the shallow, sedimentary formations where oil and gas reservoirs are generally found. The test program also included mechanical and thermal shock testing. The program was designed to be brutal in order to weed out any potential failure modes before moving on to real world drilling tests. The paper will describe how the test program was designed and the tests that were undertaken. It will also show a full set of results from the testing to demonstrate the feasibility of operation of sensors and electronics under these extreme conditions and in the previously “forbidden” region above 200°C.