When oil well drillers and inventors Howard Hughes, Sr., and Walter B. Sharp developed the rotary cone rock bit to accelerate drilling through hard rock formations, they revolutionized oil well drilling.
The earliest oil well drilling was accomplished through the use of various adaptations of the cable tool or the rod-and-drop percussion tool. As the oil-bearing formations investigated became progressively deeper, the limits of these two techniques became increasingly apparent. Although the hydraulic rotary drilling system was conceived of and in limited use as early as the 1880’s, the growth and spread of this system was almost concurrent with the Texas Spindletop
A rotary drill rig of the early twenty-first century is basically unchanged in its essential components from earlier versions of the 1900’s. A drill bit is screwed to a line of hollow drill pipe. The latter passes through a square hole on a rotary table, which acts essentially as a horizontal gear wheel driven by an engine. The drill bit itself at the hole bottom is rotated by the connected sections of the above-lying pipe in contact with the rotating table. While being rotated, the drill bit and stem are free for feeding wash water, usually an oil and mud mixture stabilized with flocculating montmorillonite clay that increases its specific gravity, to prevent side caving and to seal off water and oil-bearing subsurface strata. The mud-laden water is pumped under high pressure down the sides of the rotary drill pipe and jets out with great force through small holes in the rotary drill bit against the bottom of the borehole. This fluid then returns outside the drill pipe to the surface, carrying with it rock material cuttings from the subsurface. Circulated rock cuttings and fluids (“shale shaker”/“mud logger”) are regularly examined at the surface for evidence of the precise type and age of rock formation and for signs of oil and gas. This continual washing of drill cuttings notably reduces rig downtime compared with cable and impact tools. Rotary drilling rates usually increase as additional drill-collar weights are applied to the drill bit through the careful adjustment of drill pipe tension at the surface.
A key part of the total rotary drilling system is the drill bit, encompassing sharp cutting edges of some design that make direct contact with the geologic formations to be drilled. The first bits used in rotary drilling were paddlelike “fishtail” bits, fairly successful for softer formations, and tubular coring bits for harder geologies. In 1893, M. C. Baker and C. E. Baker brought a rotary drill rig for water wells to Corsicana, Texas, for modification to deeper oil drilling. This rig led to the discovery of the large Corsicana-Powell oil field in Navarro County, Texas. This success also motivated the rig’s operators, the American Well and Prospecting Company, to begin the first large-scale manufacture of rotary drilling rigs for commercial sale.
In the earliest rotary drilling for oil, short fishtail bits were the tool of choice, insofar as they were at that time the best configured to “make hole” over a wide range of geologic strata without needing frequent replacement. Even so, in the course of drilling any given oil well in the Gulf coast region, many bits were typically required. Especially when they encountered locally harder rock units, such as limestone, dolomite, and gravel beds, fishtail bits would typically either curl backward or break off in the hole, requiring workers to undertake the time-consuming tasks of pulling out all drill pipe and “fishing” to retrieve fragments and clear the hole. Because of the frequent bit wear and damage, numerous small blacksmith shops were established near drill rigs, where bits were dressed or sharpened by hand forge and hammer. Each bit-forging shop had its own particular ways of shaping bits, producing a wide variety of three- and four-winged bits of numerous long and short bit designs. Nonstandard bit designs were frequently modified further as experiments to meet the specific requests of local drillers encountering specific drilling difficulties in given rock layers.
In the early 1900’s, no consensus existed as to which drill bit shape was best for a given type of subsurface rock. For example, although short, one-wing fishtails drilled holes faster and cleaner in soft shales, they offered less cutting edge and less reliability than did multiwinged bits in the same material. Within a few years, several prototypes for new bits were patented; these bits variously sought to combine short cutting bases with numerous smaller cutting teeth. In 1907 and 1908, patents were obtained in New Jersey and Beaumont, Texas, for steel, cone-shaped drill bits incorporating a roller-type coring device with many serrated teeth. Later in 1908, both of these patents were bought by lawyer-driller-inventor Howard Hughes, Sr.
In 1906, with his business partner Walter B. Sharp, Hughes successfully drilled the first oil well in overpressured shales using controlled drilling mud weights. Directly motivated by his petroleum-prospecting interests, Hughes sought by trial and error to combine the best features of older and newer drill bits into one overall design that would provide greater reliability and flexibility. The general subsurface geologies encountered at the Corsicana and Spindletop fields often included complex sequences of argillaceous, arenaceous, and calcareous layers, in addition to thin stringer layers of hard anhydrites, gravels, and salt from diapiric intrusions.
Between 1885 and 1937, the American geologist R. T. Hall
Although many improvements have been made to the Hughes cone bit, in both detail and materials, since its inception in 1908, its basic design has remained in use in rotary drilling. One of Hughes’s major innovations was the much larger size of the cutters, symmetrically distributed as a large number of small individual teeth on the outer face of two or more cantilevered bearing pins. In addition, hard facing was employed to increase the usable life of the drill bit teeth. Hard facing is a metallurgical process that basically consists of welding a thin layer of a hard metal or alloy of special composition onto a metal surface to increase its resistance to abrasion and heat. A less noticeable but equally essential innovation, not included in other cone bit patents, was an ingeniously designed gauge surface that provided strong uniform support for all the drill teeth. Force-fed oil lubrication, another new feature also included in Hughes’s patent and prototypes, reduced the power necessary to rotate the bit by 50 percent over that of prior mud or water lubricant designs.
Within six years of their patents and first manufacturing, the Hughes Tool Company’s
As oil wells were drilled progressively deeper and through harder formations, a new variety of the rolling cone bit, the so-called reaming roller, was required to ensure a stable and uniformly sized drill hole. Although roll-cutter rock bits did not come into wide and regular use before the development of high-powered circulating pumps specifically for oil field service in 1915, cone bits and rotary rigs gradually replaced other drilling technologies.
This trend was notably furthered when, in 1925, the first superhard facings were used on cone drill bits. In addition, the first so-called self-cleaning rock bits appeared from Hughes, with significant advances in roller bearings and bit tooth shape translating into increased drilling efficiency. The much larger teeth made the bits more adaptable to drilling in a wider variety of geological formations than were earlier models. In 1928, Hughes metallurgists introduced tungsten carbide as an additional bit facing hardener. This, together with other improvements, resulted in the Hughes “ACME” tooth form, which has been in almost continuous use since 1926.
To further efforts in reducing drill bit wear, the Hughes company established an active and continually funded research team of mechanical engineers and metallurgists to develop methods of preparing and testing new alloys and treatments for improving the all-critical bit contact-face cutting edges. These required extensive ongoing tests over many years, a process that was comparatively uncommon in the boom-and-bust oil industry, where research and development had traditionally been the first department to be cut. In 1932, the American Petroleum Institute recommended mandatory practices for hard-facing rotary drill bits largely derived from the Hughes company’s test results. Even after Hughes’s death in 1924, part of the reason for the continued success of his rotary drill bits was his company’s ongoing effort to improve both engineering design and metallurgical composition through research.
Eventually, rotary cone rock bits increased footage drilled per hour by more than 80 percent over original figures. Many improvements in other drilling support technologies, such as drilling mud, mud circulation pumps, blowout detectors and preventers, and pipe properties and connectors, have enhanced rotary drilling capabilities to new depths (exceeding 5 kilometers, or 3.1 miles, in 1990), even permitting horizontal drilling since the mid-1980’s with the advent of down-hole motors and rotary drilling capabilities. Hughes’s successful experiments in 1908 were critical precursors to these later developments.
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Brantly, John Edward. History of Oil Well Drilling. Houston, Tex.: Gulf, 1971. The primary source for the history of the developments in rotary and other drilling methods. Very well referenced and illustrated. -
Cernica, John N. Principles of Rock Fragmentation. New York: Holt, Rinehart and Winston, 1982. An advanced undergraduate reference. Gives the theory as well as comparative laboratory field results for rock fracture under various conditions of loading and drill rotation. -
Isler, C. Well-Boring for Water, Brine, and Oil. London: E. & F. N. Spon, 1902. Notes independent and concurrent developments in rotary drilling. -
Jackson, Elaine. Lufkin: From Sawdust to Oil. Houston, Tex.: Gulf, 1982. Accurately recounts much of the economic and personal history of the early growth of the Texas oil industry. -
Jeffrey, Walter H. Deep Well Drilling. 2d rev. ed. Houston, Tex.: Gulf, 1925. Chapter 5 indicates the sequences of technical improvements associated with the wider adoption of the steel-toothed cone rotary bit. -
Paxson, Jeanette. Basic Tools and Equipment for the Oil Field. Austin, Tex.: Petroleum Extension Service, 1982. Part of a specially designed self-tutoring course on the principles and practices of rotary drilling. -
Sidorov, N. A. Drilling Oil and Gas Wells. Chicago: Imported Publications, 1986. A technical treatment of rotary drilling. Includes discussions of some of the deepest wells drilled on land.
Discovery of Oil at Spindletop
Howard Hughes Builds a Business Empire