oleocene.org

21 May 2012
One of Foro Energy's initial proofs-of-concept to establish that its high-power laser transmission platform could be used with commercial drilling equipment was achieved through the integration of its laser hardware platform with a coil tube drilling rig. This rig was used to successfully laser-mechanically drill under the ground for extended periods of time.

Laser-mechanical drilling of ultra-hard rocks is one of the major applications for high power lasers in the energy and mining industries. Conventional mechanical drill bits cut softer rocks with stresses created by rotating a cutting surface with high weight-on-bit (WOB). Unfortunately, ultra-hard (i.e., high compressive strength) rocks inherently do not yield efficiently to even the most advanced mechanical cutters. The resulting slow drilling and short bit lifetimes result in poor performance and high expense. So, they developed a process that uses the laser to first destroy the rock's strength, allowing a conventional mechanical bit to then remove the softened rock. The beam that is used to destroy the rock surface at the bottom of the borehole is shown in FIGURE 1 during a system test firing. This laser-mechanical drilling process enables: i) step changes in drilling rate (2-4x); ii) extremely low WOB (<1000 lbs); iii) extremely low torque (<300 ft-lbs); iv) longer bit life; and thus, v) lower drilling cost per foot.



FIGURE 1. Test firing of the 20 kW laser-mechanical drill
bit, as integrated into the commercial coil tube drilling rig.

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Diamond Drilling Shows its Sparkle

Over the past century, diamond drill bits have proved their worth and today remain a leading technology. Diamond drill bits were first used to drill for oil in 1863 and today, the sector has evolved into a technologically advanced and very profitable industry. The dynamics of superior performance, lower cost-per-foot and the drive for an increased rate of penetration are now more important than ever as oil prices remain far from their record highs.

Diamond drill bits are well known in the mining industry and although the basic technology may look the same, polycrystalline diamond compact (PDC) technology is specifically designed for drilling oil and gas wells. As easy-to-reach oil is becoming increasingly elusive, equipment that is effective, reliable and cost sensitive is in ever-greater demand.

Diamond drill bits are well known in the mining industry and although the basic technology may look the same, polycrystalline diamond compact (PDC) technology is specifically designed for drilling oil and gas wells. As easy-to-reach oil is becoming increasingly elusive, equipment that is effective, reliable and cost sensitive is in ever-greater demand.

Diamond drill bit manufacturing giant Baker Hughes's investor relations assistant director Gene Shiels says that PDC bits have become so advanced that their designs are now specialised to address different formations and to minimise vibration, which can lead to premature wear and slow the drilling process.

"Today there is a significant focus on drilling optimisation which is the process of looking at bit design, drilling fluids and bottom-hole assembly in concert with each other to improve drilling performance on the basis of a system as opposed to individual components," Shiels says.

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PDC bits are nothing new to the offshore industry, but the applications that they can now be used for and their increased lifespan may be. As crude oil prices remain around the $70-a-barrel mark, offshore explorers are still counting every penny and the cost of equipment is keenly felt.
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PDC bits are, by contrast, made by hand though a casting process where a graphite 'reverse mould' is constructed. "The mould is then filled with a special matrix material in combination with a binding agent and heated so that the binding agent permeates the matrix, forming the bit," Shiels says. The only way the task can be completed is by breaking the cast, adding to the cost of the manufacturing process.
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