Disposable fiber-optic system – for pipe inspection, developed by Sandia National Laboratories and Gas Technology Institute
Sandia National Laboratories, with Gas Technology Institute (GTI) funding, has developed and tested an interesting system that uses an un-armored fiber-optic cable inside the drill pipe, protected only by a thin clear plastic coating, to relay information from the bottomhole assembly sensing device to surface. The inexpensive fiber-optic string would last about 24 hours before failing, then disintegrate from mud flow and wear, and be ground up as it is washed through the bit.
The Sandia researcher, David Holcomb, who devised the technique says, “Information is instantaneously sent to surface about temperature, pressure, chemistry and the rock formation, all without stopping the drilling operation. Traditionally, this involves stopping drilling and running wireline tools. Or limited information is offered via mud pulse telemetry.”
While the details are not completely clear from a brief communication with Holcomb, it is understood that the system is run using a tool inserted in the drillstring during a connection. The lower part of the tool separates, pulling the fiber downhole from a coiled main supply. The bottom part comprises a non-contacting coil which receives data from a second coil in the BHA and transmits the information up the fiber.
At the surface, in tests so far with “singles,” the top of the system comprises another pair of coils which transmit the signal to a side-entry sub under the top drive unit, which relays information to the surface processing system. The actual fiber-optic cable placed into the drillstring weighs only about one pound. To add stands, an electrical connection, joined by a length of cable to the top of the deployment tool located below the first drill pipe connection, is broken and remade when the stand is added.
The system was tested last September at the GRI/CatoosaSM Test Facility, Inc., a GTI subsidiary, located in Catoosa, Oklahoma. The fiber was only run to 3,000 ft, but developers say it could be easily run to 10,000 ft or deeper. Reportedly, the system can transmit data at about one megabit per second, 100,000 times faster than available MWD transmission systems. David Holcomb can fill in the details and update project status. He can be contacted at tel.: 505 844 2157; email: firstname.lastname@example.org.
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COPYRIGHT 2001 Gale Group