By the OGJ Online Staff
HOUSTON, Apr. 11 -- Sandia National Laboratories said Wednesday it has developed an inexpensive disposable fiber optics telemetry system to relay real-time information about the drilling process.
David Holcomb, the researcher who devised the technique, said, "Information is instantaneously sent to the surface about temperatures, pressure, chemistry, and rock formation -- all obtained without stopping the drilling operation."
Sandia is a US Department of Energy laboratory with main facilities in Livermore, Calif., and Albuquerque, NM.
Holcomb said industry needs immediate access to downhole data without having to halt drilling. He was familiar with disposable fiber developed for the non-line-of-sight missile guidance systems in the 1980s, and realized the technology might be applied to drilling.
Using fiber optics telemetry has been expensive for the oil industry because a bulky armor was needed to protect the delicate optical fiber and deploying the cable interfered with drilling.
Holcomb's technique uses unarmored fiber protected only by a plastic coating, similar to that found in guidance systems that can deploy miles of fiber from a small spool at missile speeds.
He said, "The key difference from other attempts to insert fiber optic cable in drill pipes is to consider the cable a throwaway item, to be used once and then ground up and flushed out in the drilling mud. If the cable only has to survive for a few hours and need not be retrieved, it is feasible to use 'unarmored' fiber, which is cheap and can be wound into packages small enough to be inserted into the drill pipe without interfering with operations."
Researchers developed a tool to deploy and control the optical fiber in the rapidly moving mud in the drill string. The deployment tool weighs 75 lb and the fiber optics only 1 lb.
The disposable fiber optics system was tested last September at the Gas Technology Institute test facility at Catoosa, Okla.
Holcomb said, "We got the fiber down and the information back all successfully. While, in field tests, the optical fiber was dropped only 3,000 ft, we see no limitations. The cable could easily reach 10,000-20,000 ft."
Researchers were worried that the abrasive nature of the mud flowing through the drill string would chew up the fiber. They also were concerned that the drag of the mud flow down the drill hole would break the fiber. Neither was a problem.
The plastic coating protected the fiber and drag was not a problem, possibly because the fiber moved to the wall of the drillstring, out of the way of the mud flow.
Researchers determined the system could transmit data at about 1 megabit/sec, 100,000 times faster than measure-while-drilling systems, without interfering with the drilling process.
Sandia funded the early work and GTI the recent research. GTI is seeking industry partners to put the telemetry system into production.
