Laser Drilling Becoming a Reality

Hey Darth, Mind If We Borrow That Thing?

Not since cable tools gave way to rotary drilling almost a hundred years ago has there been a revolutionary change in drilling methods — but one may be coming.

It will, indeed, if researchers studying the potential of "Star Wars" military laser technology for use as a new drilling technique are successful.

The concept was largely a pipe dream of petroleum engineers until significant advances in laser technology were made in the 1980s and 1990s as part of the military's missile defense research.

Now researchers believe that state-of-the-art lasers have the potential to penetrate rock 10 to 100 times faster than conventional boring technologies — a huge benefit in reducing drilling costs.

And, obviously, reducing drilling costs could make previously uneconomic gas or oil reserves commercially viable.

The Gas Technology Institute initiated a two-year study in 1997 to examine the feasibility of adapting high-powered military lasers for applications in hydrocarbon exploration and production — including applications in drilling and perforating oil and gas wells.

According to a previous GTI study, 50 percent of drilling time is spent on making hole, 25 percent on tripping and 25 percent on casing and cementing. A conclusion: Major reductions in drilling costs can be achieved by faster drilling techniques and reduction in the requirements for drill string removal, bit replacement and setting casing.

So this basic research project examined the feasibility, costs, benefits and environmental impact of using lasers to drill and complete oil and gas wells.

Image Caption

A revolutionary change in drilling technology may come sooner than we realize. Researchers have determined that laser power can be effective in drilling. According to a report by the Gas Technology Institute, tests have shown that low laser power can achieve spalling or chipping; an increase in the laser power, with a fixed beam diameter results in phase changes and reactions in rock, like dehydration of clays, releasing of gases and inducing thermal stresses; and at high laser powers, the rock will melt or fuse. At even higher levels the rock will vaporize.
Photos courtesy of GTI

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Not since cable tools gave way to rotary drilling almost a hundred years ago has there been a revolutionary change in drilling methods — but one may be coming.

It will, indeed, if researchers studying the potential of "Star Wars" military laser technology for use as a new drilling technique are successful.

The concept was largely a pipe dream of petroleum engineers until significant advances in laser technology were made in the 1980s and 1990s as part of the military's missile defense research.

Now researchers believe that state-of-the-art lasers have the potential to penetrate rock 10 to 100 times faster than conventional boring technologies — a huge benefit in reducing drilling costs.

And, obviously, reducing drilling costs could make previously uneconomic gas or oil reserves commercially viable.

The Gas Technology Institute initiated a two-year study in 1997 to examine the feasibility of adapting high-powered military lasers for applications in hydrocarbon exploration and production — including applications in drilling and perforating oil and gas wells.

According to a previous GTI study, 50 percent of drilling time is spent on making hole, 25 percent on tripping and 25 percent on casing and cementing. A conclusion: Major reductions in drilling costs can be achieved by faster drilling techniques and reduction in the requirements for drill string removal, bit replacement and setting casing.

So this basic research project examined the feasibility, costs, benefits and environmental impact of using lasers to drill and complete oil and gas wells.

Some of the concerns in drilling operations are rock destruction and removal, drilling time and cost, rig size and transportation, hole shape and deviation, fishing for stuck pipe, and tripping and drilling in hard formations like granite.

"This first study was an exploratory mission to broadly look at a number of parameters and answer questions as to whether this is a feasible technology for drilling applications," said Brian Gahan, principal technology manager for the Gas Technology Institute. "In the late 1960s and again in the 1980s some published reports maintained that lasers were not effective tools for drilling, because the lasers would melt the rock resulting in high energy consumption, and penetration rates would be too low. These early authors saw lasers as a means of assisting mechanical drilling methods rather than as a stand-alone system.

"We felt that was a restrictive view of how lasers might be employed in drilling," Gahan continued, "and when researchers from the Colorado School of Mines brought this research concept to us we were very interested in pursuing it."

Can It Work?

Here's what they found: Depending on the rock type, drilling rates can be significantly reduced using lasers when compared to conventional drilling rates.

For example, lasers can penetrate hard rock — say, granite — at about the same rate as conventional techniques would penetrate soft rock.

A report on the initial research by Ramona M. Graves and Samih Batarseh with the Colorado School of Mines found that new technologies and tools operate using basic rock destruction mechanisms like thermal spalling, fusion and vaporization, mechanical stresses and chemical reactions.

"All of these destruction mechanisms," the authors wrote, "can be achieved using lasers."

At low laser power, the report said, spalling or chipping can be achieved. Increase in the laser power, with a fixed beam diameter, results in phase changes and reactions in rock, like dehydration of clays, releasing of gases and inducing thermal stresses.

At high laser powers, the rock will melt or fuse, and at even higher levels the rock will vaporize.

"Laser technology applied to drilling and completion operations has the potential to reduce drilling time, eliminate the necessity to remove and dispose of drill cuttings and improve wells performance through improved perforation operations," the report said.

We Need An Answer ...

The experimental research was designed to answer questions posed by the oil industry about laser applications in drilling. Some of these questions were:

  • What is the effect of laser power on rate of penetration and specific energy in different rock types?
  • How does lasing a rock change the permeability, porosity and elastic moduli?
  • What is the mechanism of rock destruction?
  • What is the effect of lasers on fracture formation in different rock types?
  • What is the effect of beam type - chopped, pulsed or continuous?
  • Can vertical and horizontal holes be lased with the same result?
  • What happens when saturated rocks are lased?
  • Does stress have an effect on laser-rock interaction?

Results from this initial two-year study determined that calculations significantly overestimated the energy required to spall, melt or vaporize rock.

The Tests

Regarding the initial laser drilling experiments:

  • U.S. Army's Mid-Infrared Advanced Chemical Laser (MIRACL) and the U.S. Air Force's Chemical Oxygen-Iodine Laser (COIL) systems were used. Both systems operated in the infrared optical region with power delivery capacities of one megawatt and 10 kilowatts, respectively.
  • Both lasers delivered only continuous wave beams (the COIL is now capable of pulsed beam delivery, however).
  • Laboratory tests were performed on about 150 rock samples to analyze the changes in rock properties caused by lasers. Laser-rock-fluid interactions also were studied.
  • Laser parameters like power, beam type and direction were varied.
  • Rocks used in the study included Berea sandstones, Mesaverde shaley sandstone, reservoir limestone and granite.
  • For comparison, rock properties such as porosity, permeability and acoustic properties were measured before and after lasing. Rocks were also analyzed using a scanning electron microscope combined with an energy dispersive system, thin section, X-ray diffraction and differential thermal analysis.
  • Analysis also was done under various test conditions such as type of beam, horizontal and vertical rock penetration, purge gas, saturation with water and hydrocarbons and confining stress.

Fast penetration speeds were obtained as well as some fundamental changes in the properties of the samples. For example, the porosity surrounding the lased hole in a Berea sandstone sample actually increased.

Also, the experiments indicated that at such high powers there were deleterious secondary effects that increased as hole depth increased. These effects included the melting and remelting of broken material; exsolving gas in the lased hole; and induced fractures, all of which reduced the energy transfer to the rock and, therefore, the rate of mass removal.

"However, the initial study clearly showed that laser technology is more than sufficient to break, melt or vaporize any lithology that may be encountered in the subsurface," Gahan said. "It showed that the energy required to accomplish these varies as much within lithologies as between them."

However, no quantitative results as to minimum power required or determination of factors that control power requirements were obtained.

"It became clear from these experiments, for example, that there is a need to control the amount of material melted during the laser exposure," he added, "as well as to determine quantitatively the minimum laser power needed to drill rocks for oil and gas applications."

Additional Experiments

Currently GTI, under a one-year U.S. Department of Energy cooperative agreement with Argonne National Laboratory and the Colorado School of Mines, is performing additional experiments.

A primary objective: Obtain much more precise measurements of the energy requirements needed to transmit light from the surface lasers down a borehole with enough power to bore through rocks as much as 20,000 feet or more deep.

GTI identified the specific energy requirements to remove rock from test samples of sandstone, shale and limestone.

Another aspect of the current study is to determine if sending the laser light in sharp pulses rather than as a continuous stream could further increase the rate of rock penetration. Pulsed lasers have been used for better performance in cutting steel, for example. It may be likely that the pulsing action will flex and break the physical bonds between the rock grains, boosting the cutting effectiveness.

Another element is to determine if lasers can be used in the presence of drilling fluids. The technical challenge will be to determine whether too much laser energy is expended to vaporize and clear away the drilling fluids where the actual drilling is occurring.

Later in the project, researchers could examine other uses for lasers in oil and gas drilling — such as in perforating the formations.