Cutting technology

Oct. 25, 2004
Technological advances seem to be occurring at warp speed today, compared with 15-20 years ago. Lasers, for example, have transformed the medical field and are being used in countless other applications.

Technological advances seem to be occurring at warp speed today, compared with 15-20 years ago. Lasers, for example, have transformed the medical field and are being used in countless other applications.

Efforts are under way to develop laser-based applications in the oil and gas industry as well. Lasers are already being used in pipe welding and in a laser-controlled pipe-layer. The US Department of Energy for years has been studying the technology's potential as an alternative to rotary drilling, but a working prototype is not expected until 2009.

Laser drilling would transfer energy from lasers on the surface down into a borehole via a fiber optic bundle to a series of lenses that would direct the laser light to the rock face.

"If drilling with lasers proves viable, it could be the most radical change in drilling technology in the last century," DOE said. "If" is the key word, of course.

Industry experts in the 1960s and 1970s thought lasers were too energy-intensive and inefficient to have practical applications in drilling, but there have been a number of more recent technical articles tracking progress in this endeavor.

In the most recent update, Brian Gahan presented a progress paper at the Society of Petroleum Engineers annual technical conference in Houston Sept. 26-29. Gahan is the principal exploration and production technology manager at Gas Technology Institute (GTI), which is heading a group conducting major studies for DOE.

Progress

Much US technology results from taxpayer-funded research for government projects. The government then makes the technology available for commercial development.

In 1994, Congress mandated that Cold War military technologies be transferred to American industry, including the Strategic Defense Initiative's "Star Wars" weapons-grade lasers, which DOE used to demonstrate well-construction feasibility.

GTI, Argonne National Laboratory (ANL), and the Colorado School of Mines (CSM) in 1997 began studies that, within 2 years, had disproved many earlier assumptions. ANL said the study "indicated that conventional wisdom—much of it based on 20-year-old calculations—may have significantly overestimated the energy required to break, melt, or vaporize rock." The study showed that lasers can cut all types of rock and that, in cutting rock, laser wavelength, purge gas pressure, and hole size can be as important as power.

New study

Following good results from the 1997-2000 study, DOE provided $3.1 million for a study that began in late 2000. Participants GTI, Halliburton Energy Services, and Petroleos de Venezuela SA subsidiary Intevep SA contributed $1.4 million total to the project. The research team included individuals from GTI, ANL, CSM, and Parker Geosciences.

The study attempted to determine the effects of variable pulse lasers and the correct energy requirements needed to bore through rocks as deep as 20,000 ft or more. Other issues to be addressed were drilling in the presence of fluids and the changes in energy required to remove material from water-saturated rock compared with dry rock.

Beyond 2001, the study would address the use of lasers for downhole well completion and stimulation.

The project already has specified the optimal parameters to minimize the amount of energy required to break or remove material from each rock type. GTI also determined that laser energy can cut fluid-saturated rock faster than dry rock and that pulsed lasers, which cut faster and with less energy than continuous-wave lasers, can penetrate all rock types, including granite, much faster than conventional methods.

The trials also "have substantiated that the potential exists to induce fractures in the rocks, enhancing permeability and porosity," Gahan reported.

Future work will focus on further investigations to assess the amount of specific energy absorbed by secondary processes and to determine the effects of the laser rock interaction on permeability, among other things.

In 2003, GTI refined its research focus, examining advances in fiber laser technology. It formed an alliance with IPG Photonics Corp., acquiring a 5-kw fiber laser system that now forms the heart of a new laboratory that GTI unveiled in January at its headquarters in Des Plains, Ill.

Gahan said tests with the most recent evolution of high-power lasers—a 5.34-kw Ytterbium-doped, multiclad fiber laser—indicate that the megawatt-class "Star Wars" military lasers actually are not necessary to achieve improvements in near-tunnel permeability.