IMPROVED NATURAL GAS STORAGE WELL REMEDIATION

This report summarizes the research conducted during Budget Period One on the project ''Improved Natural Gas Storage Well Remediation''. The project team consisted of Furness-Newburge, Inc., the technology developer; TechSavants, Inc., the technology validator; and Nicor Technologies, Inc., the technology user. The overall objectives for the project were: (1) To develop, fabricate and test prototype laboratory devices using sonication and underwater plasma to remove scale from natural gas storage well piping and perforations; (2) To modify the laboratory devices into units capable of being used downhole; (3) To test the capability of the downhole units to remove scale in an observation well at a natural gas storage field; (4) To modify (if necessary) and field harden the units and then test the units in two pressurized injection/withdrawal gas storage wells; and (5) To prepare the project's final report. This report covers activities addressing objectives 1-3. Prototype laboratory units were developed, fabricated, and tested. Laboratory testing of the sonication technology indicated that low-frequency sonication was more effective than high-frequency (ultrasonication) at removing scale and rust from pipe sections and tubing. Use of a finned horn instead of a smooth horn improves energy dispersal and increases the efficiency of removal. The chemicalmore » data confirmed that rust and scale were removed from the pipe. The sonication technology showed significant potential and technical maturity to warrant a field test. The underwater plasma technology showed a potential for more effective scale and rust removal than the sonication technology. Chemical data from these tests also confirmed the removal of rust and scale from pipe sections and tubing. Focusing of the underwater plasma's energy field through the design and fabrication of a parabolic shield will increase the technology's efficiency. Power delivered to the underwater plasma unit by a sparkplug repeatedly was interrupted by sparkplug failure. The lifecycle for the plugs was less than 10 hours. An electrode feed system for delivering continuous power needs to be designed and developed. As a result, further work on the underwater plasma technology was terminated. It needs development of a new sparking system and a redesign of the pulsed power supply system to enable the unit to operate within a well diameter of less than three inches. Both of these needs were beyond the scope of the project. Meanwhile, the laboratory sonication unit was waterproofed and hardened, enabling the unit to be used as a field prototype, operating at temperatures to 350 F and depths of 15,000 feet. The field prototype was extensively tested at a field service company's test facility before taking it to the field site. The field test was run in August 2001 in a Nicor Gas storage field observation well at Pontiac, Illinois. Segmented bond logs, gamma ray neutron logs, water level measurements and water chemistry samples were obtained before and after the downhole demonstration. Fifteen tests were completed in the field. Results from the water chemistry analysis showed an increase in the range of calcium from 1755-1984 mg/l before testing to 3400-4028 mg/l after testing. For magnesium, the range increased from 285-296 mg/l to 461-480 mg/l. The change in pH from a range of 3.11-3.25 to 8.23-8.45 indicated a buffering of the acidic well water, probably due to the increased calcium available for buffering. The segmented bond logs showed no damage to the cement bond in the well and the gamma ray neutron log showed no increase in the amount of hydrocarbons present in the formation where the testing took place. Thus, the gas storage bubble in the aquifer was not compromised. A review of all the field test data collected documents the fact that the application of low-frequency sonication technology definitely removes scale from well pipe. Phase One of this project took sonication technology from the concept stage through a successful ''proof-of-concept'' downhole application in a natural gas storage field observation well. The next phase of the project will demonstrate the technology in a pressurized storage field well.« less