Technology Update: The Dawn of MEMS Sensors for Directional Drilling

Abstract

Technology Update As the oil and gas industry has gone through a long downturn from which it is just now recovering, operators have heightened demands for increased downhole well intelligence, greater technology reliability, and faster drilling execution while cutting the cost of bringing wells on line. These forces together are ushering in a new era of directional drilling sensor technology that is based on microelectromechanical systems (MEMS). The fundamental mechanics and principles behind well sensor technology have changed only twice in the history of oil and gas drilling. The technology first appeared with the invention of borehole sensors in the 1920s. Until then, the industry was essentially drilling blind. The borehole instruments that were developed used simple technology such as acid in bottles that would etch its meniscus into glass, or employed other simple mechanical means, to measure the deviation of a well. In the 1970s, a major revolution swept the industry with the invention of magnetic steering tools, on whose principles most modern directional drilling tools are still based today. However, we are now witnessing the dawn of a new era as directional drilling sensors based on MEMS technology are becoming accepted as a reliable alternative for borehole surveying. Why MEMS? With MEMS humans can create microscopic mechanical devices so small as to challenge even the most vivid imagination. Imagine gears, transmissions, clutches, actuators, and even miniature turbine engines that can all fit on a fingernail (Fig. 1). But, how can one make something so small? Even modern precision computer-numerical-control machines cannot operate on the microscopic scale required to manufacture a MEMS device. The secret lies in the creative repurposing of semiconductor manufacturing techniques. Using tools built for manufacturing the microscopic transistors needed for today’s powerful computers, manufacturers can build up, layer by layer, microscopic mechanical components instead of transistors. Material deposition, layering, and patterning by photolithography to etch away the material are the key techniques in manufacturing MEMS devices. Basing MEMS manufacturing on semiconductor technologies not only miniaturizes devices to the extreme, but makes them inexpensive and rugged. Semiconductor plants are built to churn out chips, or MEMS designs, by the millions or billions. These economies of scale, the incorporation of electronics that use the same process, equipment availability, and low-cost materials make MEMS an attractive technology for the mass manufacture of sensors.