The Continuing Saga of Laser Drilling
by F. Jay Schempf
|Friday, December 05, 2003
Research into using light beams to bore wells is being redirected toward a new way to complete them, with the hope that producers will accept it all.
Recently, the Gas Technology Institute (GTI) chose short-term practicality over longer-term evolution when it comes to drilling with lasers. Instead of boring big holes, they're now concentrating on making littler ones.
Laser drilling? You know, aiming powerful light beams to burn holes in the ground instead of drilling them the old-fashioned way with conventional rotary equipment. The idea is an offshoot of the old science-fiction "death ray" chestnut that actually became a reality back in the 1970s and served as the keystone of President Ronald Reagan's Star Wars missile defense program in the 1980s--the one that set off a weapons-race cost struggle that contributed significantly to the demise of the Soviet Union.
The GTI, located in Des Plaines, IL, a Chicago suburb, is a leading research, development, and training organization serving U.S. energy markets. It was once known as the Gas Research Institute.
Since the mid-90s, the GTI has been a major player in developing a way to use lasers to make hole for gas and oil wells, among its other R&D pursuits. From the start, it teamed with government agencies, academic institutions, and private industry to pursue fundamental research, relying on the use of big, high-powered—and, because of their huge size, stationary--military lasers to blast through rock samples. They made a lot of progress, too, particularly in the last two or three years.
During this time, however, private industry began developing lasers in a big way, combining them with fiber optics to expand the new field of "photonics" into many new industrial and scientific areas. To name just two, the auto industry now cuts car body panels with them, and surgeons use them to repair human bodies.
After nearly a decade of experimenting with high-energy beams to make holes in the ground by melting, cracking, and/or vaporizing rock, the GTI and others found themselves still looking 10 years out before a workable laser drilling tool could be ready for the field. So, they decided several months ago to direct their R&D focus at a more practical kind of petroleum industry hole-making, that is, wellbore perforating--making a series of holes through steel casing and cement into the reservoir rock to allow hydrocarbons to flow into the well.
The idea behind the switch, it would seem, was that petroleum E&P has been based on rotary drilling technology for more than a century, and some major advances in that technology have been added even relatively recently. But, the thought continues, even a decade from now it probably would be exceedingly difficult to persuade the industry to try laser drilling. Developing a viable method for completing conventional wells with laser-bored perforations, however, might be an excellent way to start building acceptance of this drilling concept.
Brian C. Gahan, GTI's principal technology manager for laser drilling research, said the real impetus for concentrating on well perforating was the speed with which the photonics industry has miniaturized laser-generating equipment while increasing its power, and has combined it with the ability to send laser energy through fiber optics or other waveguide materials.
In fact, this past year GTI phased out a two-year agreement with nearby Argonne National Laboratory, a DOE research center, under which Argonne had supplied the use of its stationary 1.6-kilowatt (kw) industrial laser for the GTI group's hole-boring experiments.
The reason for the move, said Gahan, was that while the Argonne laser could be modified to work with fiber optic cable, GTI is bringing the work inhouse by dint of having acquired a 5-kw laser with built-in fiber optic transmission. It can be configured to broadcast in either a continuous or a pulsed beam, which is important to blasting through layers of rock, he added. What's more, tacking on booster modules can increase the laser's power. Finally, he noted, the new laser has a much smaller overall "footprint"--about the size of a 1960s console TV set--and can be easily moved, which would be important when eventual laser perforating field trials are conducted. The purchase price, said Gahan, was about $750,000.
But, thanks to the research conducted so far on laser well construction, the benefits of laser perforating are more than just being able to poke holes with powerful light beams, said Gahan.
Perforating producing zones with explosive shaped charges, a technology developed in the late 1950s, continues to dominate the completion process today. But the practice often has a number of drawbacks, Gahan observed. Not the least of these is significant formation damage, including reduced rock porosity and permeability (P&P) as metal and cement debris are forced into perforation tunnels by the charges' explosive effects. Additionally, pore-throat size reduction and plugging often result from fine-grain particles being forced into them by the shaped-charge explosions. And while service companies have developed various ways to stimulate increased flow and to remediate the damage created by explosive perforating, these services represent both completion delay and higher costs, he said, yet they still fail to eliminate the formation damage completely.
From evidence gained repeatedly from research so far, he continued, the lasing process actually appears to improve formation P&P.
"We've observed that photonic energy can create fluid communication channels from the reservoir to the well bore while enhancing porosity and permeability in the perforation tunnel and adjacent zones," said Gahan. "Perforating with lasers eliminates debris production and compaction of the rock formation adjacent to the tunnels. It also reduces permeability damage, and eliminates the overall health and safety concerns associated with handling explosives."
GTI has partnered with "several large well service industry companies"--make that Halliburton and Schlumberger, among others--to assist in proof-of-concept development of the laser perforating system, said Gahan. The service companies' engineering knowledge will help the group design and build a downhole tool that would carry the laser power, divided equally among fiber optic cables, down the borehole via wireline or coiled tubing to a point opposite the target formation. There, the laser beams would be concentrated continuously to penetrate the well bore's steel casing and cement, and then pulsed to cut into the formation rock without overheating and damaging tunnel walls.
Adding the new compact, portable laser to the mix promises to accelerate downhole tool development significantly, noted Gahan. With the addition of incremental power in modules, the laser's strength can be increased to from 10 to 30 kw, which Gahan said is more than adequate to transmit the beams into deep bore holes and still cut perforations effectively into pay intervals. Well site power could come from existing rig engines and/or additional engine skids.
What's more, he observed, with lasers, the size and depth of perforations can be manipulated and changed using downhole telemetry to orient cutting forces. While shaped charge perforating produces what are roughly carrot-shaped tunnels, lased perforations could be controlled to cut tunnels of different configurations to gain more exposure to the formation and to guard against tunnel wall damage due to flow depletion and formation compaction.
"We hope to complete the proof-of-concept phase by next summer," said Gahan. "After that, assuming continued progress, we could perhaps employ a tool in our test well at the Port of Catoosa, near Tulsa, OK, within two years." After that, the not-for-profit GTI presumably would license the tool, and licensees would market laser perforating to the industry.
Meanwhile, GTI and its partners would continue working to make using lasers a significant future alternative to both drilling--and completing--oil and gas wells.