That's why the R&D 100 Award-winning Oil Field Tiltmeter has such a great future, enabling explorers to determine where to put their next multimillion-dollar well to get maximum production.More than half of American oil-producing wells require help, usually in the form of cracking the underground rock to provide channels through which the oil can flow. This hydrofracturing is done by pumping a mixture of water, polymers, and sand down a well under high pressure, which causes the surrounding rock to crack and move slightly. In the past, an array of ultrasensitive tiltmeters was placed near the surface to detect the slight tilting, which reveals the primary direction of the cracking several thousand feet below. This information helps drillers decide where to sink additional wells.But these surface tiltmeters were not without problems. They could measure hydrofracturing only to a depth of 6,000 feet (1,800 meters), which excluded about 80% of the oil wells in the nation. They also were vulnerable to "noise" at the surface--wind, thermal expansion, rain, vehicle traffic, pumps, even the tidal effects of the moon and the sun. To overcome these shortcomings, oil explorers tried deploying the tiltmeters deeper in the ground, but that required manual leveling, which could not be done accurately at depths greater than 20 feet (6 meters).
Solving the Problems
Lawrence Livermore researcher David Castillo had a better idea. He and colleagues Carl Boro and Steven Hunter developed the new Oil Field Tiltmeter that is smaller, sends digital signals, takes less time to install, and costs considerably less than competing products. Working with Pinnacle Technologies in San Francisco, they brought the product to market in October 1996 as the Pinnacle 5000 Oil Field Tiltmeter--and subsequently won an R&D 100 Award for the technology.
"The tiltmeter works on the same principle as a carpenter's level," Hunter says. "The sensor is a liquid-filled glass tube with a gas bubble in it. The difference is that the tiltmeter sensor has electrodes in it so the circuitry can detect the position of the bubble."
The self-leveling mechanisms allowed a smaller tiltmeter design. For deployment at 40- to 100-foot (12- to 30-meter) depths, Hunter and the team designed their product for slim-hole technologies--wells that are only 3 inches (7.6 centimeters) in diameter. In turn, the tiltmeters benefit from more stable hole conditions because the ground is disturbed less when smaller holes are drilled. Other features of the new tiltmeter include an electronic compass for instrument orientation, a downhole analog-digital converter to reduce electronic noise, and an internal data logger with a large memory.
The signal from the new tiltmeter goes to a differential amplifier, is rectified (made to flow in one direction only), and is further amplified. After it is filtered, the signal is digitized by a 24-bit converter, which provides a signal with higher resolution than previously used 16-bit converters. This digitized signal is much less susceptible to electronic noise and thus results in much more reliable data, which are stored in a random-access memory device until a technician downloads it to a lap-top computer.
