The US Department of Energy (DOE) and industry sponsors have teamed up to put "sonification" to the test.
For a long time - more than 50 years, actually - producers have been interested in sonic reservoir stimulation. Basically, the technique involves transmitting sound waves through a producing formation to free trapped oil. More recently, it has been used in actual wells, successfully in some cases and not so successfully in others.
In the 1950s, water well drillers noticed seismic excitation produced by passing railroad trains and distant earthquakes resulted in a rise in well fluids and increases in pore pressures. In later years, inquiries into this phenomenon graduated into actual field experiments. The Russians, for instance, tested the idea in the 1980s by placing surface seismic vibrators above oil fields. The results were mixed. Since then, a handful of companies have offered sonic stimulation tools and mechanisms. Overall, the tools are said to produce promising, but inconsistent, results.
Nevertheless, several research projects and field demonstrations have been created, using various tools under actual field conditions. Once again, results have been mixed. The problem all along, apparently, has been that little empirical evidence exists about how the process works.
So the federal government, industry and academia recently partnered up to produce just such evidence. The impetus behind this new research effort is improving recovery from domestic oil fields, with the goal being to reduce the nation's dependency on oil imports from, as they say, "less secure" sources.
In November 2001, DOE's Office of Fossil Energy anted up about US $1 million to go with another $250,000 pledged by industry for a 36-month project aimed at calibrating and testing "sonification," as they call it. The goal is to establish a more solid theoretical basis for the technology.
The DOE chose Michigan Technological University (MTU) at Houghton to conduct the hands-on research. Heading up the MTU activities are three academics considered to be top experts in sonification: Wayne Pennington and Roger Terpening, both Ph.D.s at MTU, and Igor Beresnev, Ph.D., of Iowa State University.
Industry partners include Sonic Production Systems, Ames, Iowa; Wave Energy Resources Inc., Denver, Colo.; and Well Seismic Computing Services, Newport Beach, Calif. Baker Hughes' Baker Atlas unit also is involved.
The project is designed to provide the linkage between field and theory, and between laboratory experiments and field demonstrations, DOE said. First, the research will explore the penetration factors associated with multiple frequencies, both at and below the surface. This will include testing the performance of two sonification tools, one that applies wireline-conveyed power and another that uses tubing-conveyed, high-pressure water to generate sonic waves.
A well test facility operated by MTU in the northern Michigan reef trend will serve as the primary site for all field work. Two boreholes will be used - a source well for the tools and a receiver well fitted with multiple levels of clamped geophones and hydrophones.
After completing testing and setting calibration standards, the MTU researchers will broaden the project scope to include other manufacturers and service companies who may be interested in testing their sonic tools or processes in a well-defined, controlled environment, DOE said. A series of technology transfer workshops also will take place, since with tax-dollar-assisted industry projects such as these, the results must be made available to the industry at large.
The ultimate goal is a unified set of standards by which sonic stimulation technology can be applied. Such standards would be the basis for improving tool design and optimizing field operations, and would allow theoretical and laboratory work to move ahead with more confidence.
Roy Long, product manager for petroleum exploration and production at DOE's National Petroleum Technology Office (NPTO) in Tulsa, Okla., said that while the MTU-directed project gets under way, actual field testing of sonification technology is being done. For example, he said, Phillips Petroleum and others are testing a tool in the North Burbank Unit in Oklahoma. Several other joint industry laboratory research efforts - using cost-shared funds provided by DOE - also are ongoing. In the recent past, ChevronTexaco and Aera Energy tried field demonstrations in several California heavy oil fields, and Marathon has given it a try in the Tensleep formation in Wyoming. Finally, BP is said to have chosen five onshore, low-gas-content candidate reservoirs in "softer" rocks for future tests.
"We're all trying to understand what's going on," said Long. "If the technology has application, obviously we're going to try some demos with it. Potentially, it might go beyond tertiary recovery. It might even be used during or before secondary recovery. However, we need to establish baseline standards for what to expect. We need a much better handle on where we can use sonification technology and what really is happening downhole. That's why the research at MTU is so important."

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