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This paper was prepared for the 92nd AIME Annual Meeting in Dallas, Texas, February 24–28, 1963, and is considered the property of the Society of Petroleum Engineers. Permission to published is hereby restricted to an abstract of not more than 300 words, with no Illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Technology or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request providing proper credit is given that publication and the original presentation of the paper.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

A discussion having the title "Steels for Drill Pipe, Tool Joints, and Drill Collars" written by a user is naturally a discussion of significant problems arising from usage of these drill string items. The discussion that follows indicates user problems that may or may not be solved by metallurgical improvements.

PENETRATION RATE FACTORS

A way to reduce drilling cost is to drill faster. The following is a simplified expression of the drilling rate equation:

R =

Cf = Drillability coefficient W = Bit weight N = Rotary speed D = Bit dullness

Thus drilling rate increases with drillability, weight, and rotary speed, and decreases with dullness. The bit weight and rotary speed exponents vary with the type of formation being drilled and are of such value that a point can be reached where further increase results in no better rate of penetration.

The bit weight and rotary speed that will yield maximum performance depends in part upon the ability to clean the hole ahead of the bit. This is the function of rig hydraulic horsepower that generally accounts for use of higher circulating pressure and the consequent demand for larger pumps.

Rock bits have been improved to withstand higher weight and more rotary speed. The steel is tougher so teeth don't break off quite so readily. This fact permits use of a longer toothed bit that produces a faster drilling rate.

Growing effort to achieve a faster drilling rate by use of increased bit weight, rotary speed, hydraulic horsepower and bits with more bottomhole action has created drill string deterioration and failure problems of considerable proportions.

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