Downhole Electronic Components: Achieving Performance Reliability

Abstract

Electronic Component Reliability Measurement-while-drilling (MWD) tools were introduced to the oil and gas industry in 1978 by what was then known as Teleco Oilfield Services (bought by Baker Hughes in 1992). Ever since, the industry has had to contend with designing computer circuit boards populated with electronic components that must perform reliably under a combination of extremely harsh downhole conditions. The primary hostile conditions are temperature, variable amounts of vibration, and intermittent shock. Additionally, designers must consider the limitations of the downhole batteries and alternators used to power the electronic assembly. This combination of conditions, in fact, is at least as demanding than those encountered in the defense, space, aeronautics, and automotive industries. Electronic components include capacitors, resistors, inductors, transistors, oscillators, resonators, semiconductor chips, processors, and memory chips. The bulk of the electronic component market serves commercial needs. “Even though it’s come a long way in the last 10 to 15 years,” said Matthew White, director of engineering at Ryan Directional Services, “still I would estimate that 85% of the integrated circuits [ICs] and parts on the market today are rated at 85ºC. And another 10% to 12% are rated to 125ºC. Maybe 2% or 3% are rated anything above that.” With downhole temperatures routinely reaching 150ºC to 175ºC within the deep shale plays in the United States, and offshore downhole temperatures reaching as high as 200ºC, particularly in southeast Asia, the industry demand for reliable MWD and formation-evaluation-measurement-while-drilling (FEMWD, also known as logging-while-drilling or LWD) tools continues unabated. The problem is that the oil and gas industry’s demand for high-temperature electronic components is comparatively tiny—combined with defense, space, aeronautics, and automotive, estimated to be less than 1% of the total component market. Additional splintering of demand results from individual oilfield services companies keeping exclusive agreements with component manufacturers secret. “I’m more of the opinion,” said Robert Estes, manager of emerging technology, Drilling & Evaluation at Baker Hughes, “that we have to encourage the development of components that can be shared between military, aerospace, automotive, oilfield operations, and geothermal.” Aaron Schen, department manager of the Electronics Development Group (Downhole) at National Oilwell Varco (NOV), notes that, generally, non-semiconductor downhole components such as sensors and connectors are pretty well supported by vendors. “It is routine to find high-temperature, high-severity, and high-pressure (if needed) ratings for those types of components,” he said. He contends this is because a small, niche-market company “can be happy making a couple hundred pressure sensors a year. Chips are turned out in the millions.”