Fake diamonds find oil field fans

Diamonds are fast becoming an oil man's best friend. But unlike Carol Channing in "Gentlemen Prefer Blondes," oil men are not sporting these sparklers on their fingers. They are putting them on drilling bits in order to save money and sink wells more quickly.

Synthetic diamond drill bits are the first major innovation to hit the oil drilling industry since the turn of the century when Howard Hughes Sr. invented the "roller cone" bit.

This bit, which quickly became the industry standard, crushes and gouges its way through rock. The roller-cone bit was a major advance over previous, hammering-type drills and has reigned supreme in what is now a $1 billion per year market for drilling bits.

The diamond bit is its first real competitor, say industry sources. This type of bit grinds perpendicularly into rock, as a milling tool cuts metal. Although the use of industrial diamonds on drilling bits has been around for some time, it was not until 1976 that a division of the General Electric Company produced a new, significantly strengthened type of synthetic diamond which made diamond bits competitive with the roller-cone.

The new bits are made with tiny pieces of wafer-shaped diamond -- one-half inch in diameter and an eighth inch thick -- planted on a tungsten-carbide backing. These are brazed onto a flat-headed bit.

The diamond bits are significantly more expensive than those of conventional design. But in softer rock formations this cost appears to be more than offset by longer life and faster drilling rate.

The diamond bits have shown penetration rates as much as four times that of conventional bits," says Sam Varnado, supervisor of the milling technology division of SandiaLaboratories, a Department of Energy research facility which helped in the development of diamond bits.

With the cost of operating an oil drilling rig running between $50,000 to $ 100,000 a day, the time saved by faster drilling speeds and fewer bit changes has created considerable interest in the industry.

The jury is still out on the merits of diamond bits for hard rock, such as granite, says Mr. Varnado. While they do drill faster, they wear out faster as well. They also have a problem with the diamond teeth knocking loose.