ALBUQUERQUE, N.M. — The results of a series of field tests carried out at six producing U.S. oil wells are now available to members of the petroleum industry on a free CD-ROM put together by Sandia National Laboratories.
Called the Downhole Dynamometer Data Base (DDDB), the CD-ROM contains more than 60 megabytes of data gleaned from a downhole diagnostic tool that measures actual stresses along sucker rod strings used to extract crude oil from approximately 80 percent of domestic oil wells.
Sandia’s work was sponsored by the Department of Energy’s National Gas and Oil Technology Partnership, a program designed to bring national laboratory resources to bear on technical problems identified by the U.S. petroleum industry.
The new tool, called the downhole dynamometer, is a foot-long, cylindrical steel probe, several of which can be integrated into a sucker rod string and sent deep into a pumping well. A series of sensors distributed along each probe’s surface — including strain gauges, an accelerometer, and pressure and temperature gauges — gathers information from the well bore during pumping. The raw data can be saved in the tools’ memory chips for months at a time until the sucker rod string is extracted from the well, most often during normal maintenance periods. The dynamometer’s development was completed in March 1995.
From this data, researchers and well operators can extrapolate valuable information about well bore dynamics and mechanical stresses on sucker rod strings that often lead to equipment fatigue and rod failure — most significantly from the repeated compression, bending, and buckling strains on a sucker rod as it bangs against well tubing and works against the resistance of crude oil surrounding the rod on each downstroke.
Because sucker rod failure represents a significant cost to the oil recovery industry, Sandia researchers hope the information contained in the DDDB can be used to improve the load-versus-position codes oil well operators use to determine sucker rod design and, ultimately, help operators optimize sucker rod string taper, weight, and other factors for a variety of wellbore environments.
“Sucker rod pumping accounts for most of the United States’ domestic oil production,” says Bob Cutler of Sandia’s Advanced Geophysical Technology Department, “so anything that improves the efficiency of sucker rod operations is significant for a healthy domestic oil and gas industry.”
In the past, he says, operators have relied on load-versus-position information measurable at the surface to extrapolate stresses on sucker rod strings deep underground. “This new data should give operators a lot of previously unmeasurable information about what actually goes on in the well bore and allow for more efficient pumping operations,” he says.
Sandia and Nabla Corp. (Midland, Tex.) conducted the field tests from February through December 1996 at U.S. oil wells featuring a variety of pumping conditions. “We chose well environments and operating conditions that are representative of what would be encountered in the field,” Cutler says.
During each test, five downhole dynamometers were incorporated into a sucker rod string at depths ranging from the surface to 9,600 feet, depending on the depth of the well, known well bore conditions, and the pumping equipment being used.
All the data from the tests are now available on a single CD-ROM disk, free to members of the U.S. oil and gas industry. The Sandia CD-ROM features easy-to-use, industry-tested interface and graphing utilities that allow the user to generate load-versus-position dynagraphs from data collected down hole. The interface can be used with Microsoft Windows 3.11, Windows 95, and Windows NT; instructions for installation and use are included.
A variety of oil-industry players could benefit from this data, says Chip Mansure of Sandia’s Geoscience and Geotechnology Center, including pump equipment manufacturers, well operators, and sucker rod manufacturers and service companies.
Technology for the downhole dynamometer diagnostic tool was originally developed by Glen Albert, founder of Albert Engineering (Longmont, Colorado). Sandia, at the request of the Natural Gas and Oil Technology Partnership Sucker Rod Working Group, commissioned further development of the dynamometer by Albert Engineering, coordinated the field tests, and created the DDDB and its graphical user interface.
Results of the field tests have been presented at meetings of the Society of Petroleum Engineers and at the Southwest Petroleum Short Course.
Sandia is a multiprogram Department of Energy laboratory operated by a subsidiary of Lockheed Martin Corp. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has broad-based research and development programs contributing to national defense, energy and environmental technologies, and economic competitiveness.
To receive a free copy of the CD-ROM or collaborate with Sandia on future work, contact Bob Cutler at 505-844-5576; at rpcutle@sandia.gov; or at Sandia National Laboratories, P.O. Box 5800, Mail Stop 0705, Albuquerque, N.M. 87185-0705. (To receive the CD-ROM, you must agree to abide by some restrictions, such as agreeing not to incorporate the data base into another commercial product.)