Laser drilling may be key to make previously uneconomic oil or
gas deposits commercially attractive as Argonne National Laboratory (Laser
Applications Laboratory) and a group of collaborators are examining the
feasibility of adapting high-power laser technology to drilling for gas and
oil.
The initial phase is designed to establish a scientific basis
for developing a commercial laser drilling s
ystem and determine the level of gas industry interest in
pursuing future research. If drilling with lasers ultimately proves viable, it
could be the most radical change in drilling technology in the last century.
It was at the turn of the 20th century when rotary drilling
supplanted cable tool drilling as the petroleum industry’s standard method for
reaching oil and gas formations. While major improvements have occurred since
then, the basic mechanical drilling method has remained essentially the same.
Using lasers to bore a hole offers an entirely new approach. The
novel drilling system would transfer light energy from lasers on the surface,
down a borehole by a fiber optic bundle, to a series of lenses that would
direct the laser light to the rock face.
Drilling Many Times Faster
Researchers believe that state-of-the-art lasers have the
potential to penetrate rock many times faster than conventional boring
technologies – a huge benefit in reducing the high costs of operating a drill
rig.
Today, a typical land-based oil or gas well costs around
$400,000 to drill, while costs for an offshore well average nearly $4.5
million. But in some deeper or more difficult drilling terrains, costs can be
much higher. Reducing the time a drill rig remains on site can lower costs and
make previously uneconomic gas or oil deposits commercially attractive.
The earlier study showed that laser systems now can provide more
than enough power to cut rock. Because the laser head does not contact the
rock, there is no need to stop drilling to replace a mechanical bit.
Moreover, researchers believe that lasers have the ability to
melt the rock in a way that creates a ceramic sheath in the wellbore,
eliminating the expense of buying and setting steel well casing. A laser system
could also contain a variety of downhole sensors – including visual imaging
systems – that could communicate with the surface through the fiber optic
cabling.
Changing Conventional Wisdom
While the lure of laser drilling has been its speed, one major
drawback has been the large amounts of energy experts assumed would be
required. The 1997-99 Gas Research Institute study indicated, however, 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.
One of the primary objectives of the new study will be to obtain
much more precise measurements of the energy requirements needed to transmit
light from surface lasers down a borehole with enough power to bore through
rocks as much as 20,000 feet or more below the surface.
Another aspect of the study will be 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 laser 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.
A third aspect of the new project will be to determine if 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 clear away the fluid where the drilling is
occurring.
Later in the project, researchers could examine other ways to
use lasers in oil and gas drilling. For example, after a well is drilled,
perforations are created into the formation to start the flow of hydrocarbons.
Part of the research effort will study ways lasers could be used to create
these perforations.
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