The viability of using high-power lasers—including some originally conceived for the "Star Wars" missile defense concept—to drill for oil and gas is being investigated by the Gas Technology Institute (GTI; Des Plaines, IL) and the US Department of Energy's (DOE) National Energy Technology Laboratory (Morgantown, WV), in collaboration with industry partners. If drilling with lasers proves feasible, it will be the most radical change in drilling technology in more than 100 years.
In theory, a laser drilling system would transfer light energy from lasers on the surface down a borehole by a fiberoptic bundle, to a series of lenses that direct the laser light to rock.
State-of-the-art lasers have the potential to penetrate rock at 10 to 100 times faster than conventional boring technologies—a huge benefit in reducing the high costs associated with operating a drill rig. Researchers believe that lasers also have the ability to melt rock in a way that creates a ceramic sheath in the wellbore, eliminating the expense of buying and setting steel well casing. In downhole measurement applications, the laser head could even be equipped with sensors such as televiewers and other image logs for continuous, high-speed communication of data with the surface.
"Now is the time to introduce a fundamental improvement in drilling systems," says Brian Gahahn, project principal investigator, GTI. "We're hopeful that encouraging results from the study will generate industry interest in supporting the development of a prototype laser drilling tool."
In related studies conducted in 1997, more than 200 samples of various lithologies were exposed to a range of power levels, wavelengths, durations, and beam diameters. Three laser systems were tested, including the US Army's Mid-Infrared Advanced Chemical Laser (MIRACL); the US Air Force's Chemical Oxygen/Iodine Laser (COIL); and a Laser Hardening Material Experimental Laboratory Carbon Dioxide Laser. Of the three systems, MIRACL and COIL showed the most promise as drilling lasers. MIRACL, developed for shipboard defense and used extensively to test "Star Wars" concepts during the 1980s and 1990s, is the highest average-power laser (megawatt class) in the US. It operates at a wavelength of 3.8 µm and has the demonstrated power levels needed to burn through solid materials such as soft rock minerals. COIL, originally developed as an airborne laser tactical weapon, is a high-powered laser that operates at a wavelength of 1.3 µm with a precision that could be applied to drill and complete wells at depths of more than 15,000 ft.
During the next three years, the project's researchers will focus on three fundamental research areas—laser-cutting energy assessment, variable-pulse laser effects, and laser drilling under fluid conditions.
The laser-cutting energy assessment will be developed by obtaining precise measurements of the energy requirements needed to transmit light from surface lasers down a borehole with enough power to bore through rocks 20,000 ft or more below the surface.
Variable-pulse laser effects will be tested to determine whether sending the laser light in sharp pulses, rather than as a continuous stream, could further increase the rate of rock penetration. The pulsing action may flex and break the physical bonds between the rock grains, boosting the cutting effectiveness.
Laser drilling under fluid conditions will be investigated to determine whether lasers can be used in the presence of drilling fluids. In most wells, thick fluids—called "drilling muds"—are injected into the borehole to wash out rock cuttings and keep water and other fluids from the underground formations from seeping into the well. The technical challenge will be to determine whether too much laser energy is expended to vaporize and clear away the fluid at the drill site.
Also participating in the research effort are the Colorado School of Mines (Golden, CO), DOE's Argonne National Laboratory (Argonne, IL), Halliburton Energy Services (Dallas, TX) and Petroleos de Venezuela, SA (Caracas, Venezuela).
