Sonic waves help recover natural gas from clogged storage sites

Could mean more gas for consumers during winter

The 10-pound sonic tool is intended to remove scale from gas storage wells.

Morgantown, WV - Natural gas companies looking for better ways to unclog the wells they use to withdraw gas from underground storage reservoirs may soon be getting "good vibes" from a low-cost sonic cleaning tool.

A Department of Energy-sponsored team of companies led by Furness-Newburge Inc. of Versailles, KY, has produced a prototype of a system that uses sound waves to remove inorganic matter and other debris that clog the perforations of gas wells.

The technology has the potential to increase significantly the efficiency at which natural gas is withdrawn from storage reservoirs, making a larger amount of gas available to consumers during the winter heating season.

The prototype was developed through a cooperative agreement between Furness-Newburge, Nicor Technologies and TechSavants Inc., both of Naperville, IL, Baker Atlas, Houston, TX, and the department's National Energy Technology Laboratory.

Composed of an oscilloscope, a power supply, a wire line reel for the power cable, an acoustical transducer, a portable generator and waterproof connections, the device is about two feet in length, two inches in diameter, and weighs about 10 pounds.

The tool is lowered into a well where it emits relatively low-frequency, high-intensity directed sound waves. After a relatively short time, the sound waves force scale surrounding the well's opening to fall off.

"Who would have thought that the Navy acoustical training I received in 1966 would be used to clean out gas wells!" said Jim Furness, principle investigator and partner at Furness-Newburge.

The basis for this device stems from a process that Furness helped develop using acoustics to catalyze ozone and peroxide to prevent air pollution in foundries.

The technology is not ultra-sound, Furness points out, "People can hear the sound used for the process." The device is tunable within the range of subsonic to 3kHz.

About two years of laboratory and bench-scale development yielded a prototype that achieved impressive results during testing last year at the Bashore No. 1 Observation Well, operated by Nicor Gas near Pontiac, IL. More extensive field tests need to be performed along with additional laboratory work before the tool can be used commercially, but results so far have been encouraging.

On average, more than 17,000 gas storage wells lose 5 percent of their ability to inject and withdraw gas from underground storage fields each year. A Department of Energy-Gas Research Institute study found that inorganic precipitate or scale was a leading cause of the problem. Inorganic matter such as calcium carbonate coats a well's openings from which gas is withdrawn. Over time, production can decline to the point where over half of the field's deliverability can be lost. The gas industry spends between $60 million and $100 million a year trying to correct this problem.

Water analyses were conducted during the field tests demonstrated the device's effectiveness in removing key constituents found in storage well deposits. Water samples collected after the sonication tool was used were compared with samples taken two months earlier. The water chemistry indicated a significant increase in mineral salts as well as increased levels of suspended matter - signs that the sonic cleaning device was doing its job.

The amount of calcium, magnesium, iron, and bicarbonate in solution increased by 100 percent, 60 percent, 60 percent, and 5,300 percent, respectively, after sonication. The amount of suspended solids also increased by 230 percent after sonication.

The acoustic portion of the tool is expected to sell for less than $15,000 and is compatible with standard wire-line equipment used routinely in day-to-day field operations.

The second phase of the research will begin this summer. Along with improving the tool so that it can operate with more rugged field handling, more field testing will be done in different types of gas storage reservoirs. Also, more definitive testing, such as gas-pressure changes, will be performed to better quantify the system's performance.