Norwegian Oil Policy and Economic Outlook: A Study of a Country in Energy Surplus
Authors: Frognes Gunnar 
Published: December 2007

From the first field tests in The Netherlands in late 1975, a new family of high-performance synthetic polycrystalline diamond compact bits has been developed. Following a progression of major efforts to develop a commercially proven product, the breakthrough was achieved in early 1978 in The Netherlands. Additional successes in the Northern North Sea led to rapidly increased applications with turbine drilling. Because of the sharp cutting edges of the synthetic diamond cutters, high penetration rates could be obtained with relatively light drilling weight, requiring fewer drill collars. The maximum rate of penetration (ROP) with these bits was achieved in oil-base mud running with turbines. Field tests confirmed laboratory tests showing that as future turbine speeds are increased, the operator will achieve even greater cost reduction. Recent field tests also indicate a significant economic potential for rotary drilling applications in certain formations. Further development work is required to improve the performance in sticky shales drilled with water-base mud. Additional improvements on the synthetic diamond cutters are needed for broader applications in medium hard and abrasive formations.

Introduction

The first downhole testing outside the U.S. with a new generation of stud-type synthetic diamond cutter-bits was done in the North Sea in Sept. 1975. The first test bit drilled with a remarkably high ROP, 62 ft/hr for 3.0 hours. The second test bit drilled 124 m in 11.25 hours, resulting in an ROP of 36 ft/hr in anhydrite and salt formations. These initial tests indicated high potential for good rates with light bit weight. Drilling speeds were three to four times higher and required only 30% of the weight on bit (WOB) needed with rock bits. The main problem that these first diamond compact bits encountered was loss of cutters resulting from inadequate bonding techniques. Starting in 1975, an intensive development effort was undertaken jointly by a major European oil company and Christensen Inc., to develop a commercially suitable product. With the success of this program in 1977 and 1978, improved diamond compact bits were used for rotary applications on a larger scale in The Netherlands, to drill anhydrite and salt formations. Also during this period, tests with downhole turbines gave encouraging results drilling Cretaceous and Jurassic formations. In the North Sea (where performance, although acceptable, did not yield the lowest cost per foot) a technical breakthrough was achieved in the first quarter of 1979, when drilling with synthetic polycrystalline diamond compact bits on turbines in oil-base mud became successful. Since that date, the use of diamond compact bits has been expanding rapidly, especially when turbine drilling with oil-base mud in the northern North Sea. Furthermore, excellent results have been obtained with diamond compact bits (both rotary and turbine) with water-base mud on- and offshore Netherlands. The results achieved in the Middle East during 1980 showed outstanding savings when using diamond compact bits for drilling formations such as limestone, chalk, marl, dolomite, and certain shales. During the last quarter of 1980, more than 20% of the total footage of 8 1/2- and 12 1/4-in. hole in The Netherlands was drilled with diamond compact bits using turbine or rotary drilling techniques. A recent record run (where a diamond compact Type 4W bit drilled the complete 12 1/4-in. section from 8,297 to 15,099 ft in 486.5 hours) resulted in savings of $195,370.

JPT

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