The invention: A rotary cone drill bit that enabled oil-well drillers to penetrate hard rock formations.
The people behind the invention:
Howard R. Hughes (1869-1924), an American lawyer, drilling
engineer, and inventor Walter B. Sharp (1860-1912), an American drilling engineer,
inventor, and partner to Hughes
Digging for Oil
A rotary drill rig of the 1990′s is basically unchanged in its essential components from its earlier versions of the 1900′s. A drill bit is attached to a line of hollow drill pipe. The latter passes through a hole on a rotary table, which acts essentially as a horizontal gear wheel and is driven by an engine. As the rotary table turns, so do the pipe and drill bit.
During drilling operations, mud-laden water is pumped under high pressure down the sides of the drill pipe and jets out with great force through the 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 below. Circulated rock cuttings and fluids are regularly examined at the surface to determine the precise type and age of rock formation and for signs of oil and gas.
A key part of the total rotary drilling system is the drill bit, which has sharp cutting edges 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 coringbits for harder surfaces. In 1893, M. C. Baker and C. E. Baker brought a rotary water-well drill rig 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 its 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 at being able to bore through a wide range of geologic strata without needing frequent replacement. Even so, in the course of any given oil well, many bits were required typically in coastal drilling in the Gulf of Mexico. Especially when encountering locally harder rock units such as limestone, dolomite, or gravel beds, fishtail bits would typically either curl backward or break off in the hole, requiring the time-consuming work 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 black shops established themselves near drill rigs, dressing or sharpening bits with a hand forge and hammer. Each bit-forging shop had its own particular way of shaping bits, producing a wide variety of 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.
SPEEDING THE PROCESS
In 1907 and 1908, patents were obtained in New Jersey and Texas for steel, cone-shaped drill bits incorporating a roller-type coring device with many serrated teeth. Later in 1908, both patents were bought by lawyer Howard R. Hughes.
Although comparatively weak rocks such as sands, clays, and soft shales could be drilled rapidly (at rates exceeding 30 meters per hour), in harder shales, lime-dolostones, and gravels, drill rates of 1 meter per hour or less were not uncommon. Conventional drill bits of the time had average operating lives of three to twelve hours. Economic drilling mandated increases in both bit life and drilling rate. Directly motivated by his petroleum prospecting interests, Hughes and his partner, Walter B. Sharp, undertook what were probably the first recorded systematic studies of drill bit performance while matched against specific rock layers.
Although many improvements in detail and materials have been made to the Hughes cone bit since its inception in 1908, its basic design is still used 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 drill bit teeth to increase usable life. Hard facing is a metallurgical process basically consisting of wedding a thin layer of a hard metal or alloy of special composition to a metal surface to increase its resistance to abrasion and heat. A less noticeable but equally essential innovation, not included in other drill bit patents,
was an ingeniously designed gauge surface that provided strong uniform support for all the drill teeth. The force-fed oil lubrication was another new feature included in Hughes’s patent and prototypes, reducing the power necessary to rotate the bit by 50 percent over that of prior mud or water lubricant designs.
Howard R. Hughes
Howard Hughes (1905-1976) is famous for having been one of the most dashing, innovative, quirky tycoons of the twentieth century. It all started with his father, Howard R. Hughes. In fact it was the father’s enterprise, Hughes Tool Company, that the son took over at age eighteen and built into an immense financial empire based on high-tech products.
The senior Hughes was born in Lancaster, Missouri, in 1869. He spent his boyhood in Keokuk, Iowa, where his own father practiced law. He himself studied law at Harvard University and the University of Iowa and then joined his father’s practice, but not for long. In 1901 news came of a big oil strike near Beaumont, Texas. Like hundreds of other ambitious men, Hughes headed there. By 1906 he had immersed himself in the technical problems of drilling and began experimenting to improve drill bits. He produced a wooden model of the roller-type drill two years later while in Oil City, Louisiana. With business associate Walter Sharp he successfully tested a prototype in an oil well in the Goose Creek field near Houston. It drilled faster and more efficiently than those then in use.
Hughes and Sharp opened the Sharp-Hughes Tool Company to manufacture the drills and related equipment, and their products quickly became the industry standard. A shrewd business strategist, Hughes leased, rather than sold, his drill bits for $30,000 per well, retaining his patents to preserve his monopoly over the rotary drill technology. After Sharp died in 1912, Hughes changed the company to the Hughes Tool Company. When Hughes himself died in 1924, he left his son, then a student at Rice Institute (later Rice University), the company and a million-dollar fortune, which Hughes junior would eventually multiply hundreds of times over.
Impact
In 1925, the first super hard facing was 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 were more adaptable to drilling in a wider variety of geological formations than earlier models. In 1928, tungsten carbide was introduced as an additional bit facing hardener by Hughes metallurgists. This, together with other improvements, resulted in the Hughes ACME tooth form, which has been in almost continuous use since 1926.
Many other drilling support technologies, such as drilling mud, mud circulation pumps, blowout detectors and preventers, and pipe properties and connectors have enabled rotary drilling rigs to reach new depths (exceeding 5 kilometers in 1990). The successful experiments by Hughes in 1908 were critical initiators of these developments.
See also Geothermal power; Steelmaking process; Thermal cracking process.
