Oil Drilling Equipment | Research & Encyclopedia Articles

Oil Drilling Equipment

Before 1859, people drilled wells in search of water, salt, or brine (saltwater). Salt was especially important to early settlers in America because it was used to preserve food. In Pennsylvania, wells often became contaminated with oil, a nuisance to salt producers. But in the mid-1800s kerosene, a product of crude oil, was discovered. Kerosene proved to be an excellent fuel for oil lamps, which were then an important source of illumination. Samuel Kier, a salt producer whose well had been ruined by the seeping oil, began selling oil-burning lamps to provide a market for his unanticipated product. He also promoted the use of mineral oil as a medicine.

About this time, two American businessmen, George Bissell (1821-1884) and Jonathan Elvereth, became intrigued with the possibilities of producing more oil for the lighting market. In 1854 they formed a partnership, the Pennsylvania Rock Oil Company, the world's first oil company. They tried to drill for oil, but went bankrupt in 1857. In 1858, a group of investors formed the Seneca Oil Company, which hired a retired railroad conductor, "Colonel" Edwin L. Drake (1819-1880), as partner and supervisor of their first drilling project. Drake had studied the methods used for drilling brine and thought that the same equipment might be used to find oil. At first, Drake and his crew struck water, which threatened to flood out the well. But Drake developed the idea of driving iron pipe down into the hole to shore up the sides and keep the water out. This basic concept is still used in oil drilling today. The following spring, Drake hired William ("Uncle Billy") Smith and his sons, who were experienced in drilling deep salt wells. The crew drilled almost seventy feet (21 m) down before they finally struck oil in 1859, and America's oil boom, and the world's oil industry, was launched. Drake and other prospectors of the day used the same equipment and method--called cable-tool or percussion drilling--that had been used for salt wells. In percussion drilling, the hole is literally punched into the ground by a heavy cutting tool, called a bit, that is attached to a cable and pulley system. The cable hangs from the top of a four-legged framework tower called a derrick. Over and over again, the cable raises and drops the drill bit, shattering the rock into small pieces, or cuttings. Periodically, these cuttings have to be wet down and bailed out of the hole. By the late 1800s, steam engines had become available for cranking the drill bit up and down and for lowering other tools into the hole.

Although this method is sometimes still used for drilling shallow wells through hard rock, most wells today are bored into the earth by rotary drilling equipment, which works like a corkscrew or carpenter's drill. Rotary drilling originated during the early 1900s in Europe, where the ground is typically softer than in America. In rotary drilling, a large, heavy bit is attached to a length of hollow drill pipe. As the well gets deeper, additional sections of pipe are connected at the top of the hole. The taller the derrick, the longer the sections of drill pipe that can be strung together. Although early derricks were made of wood, today's are constructed of high-strength steel. The whole length of pipe, or drillstring, is twisted by a rotating turntable that sits on the floor of the derrick. When the drill bit gets worn down, or when a different kind of bit is needed for a new layer of earth, the whole drillstring must be pulled out of the hole to change the bit. Each piece of pipe is unscrewed and stacked on the derrick. As the oil-bearing formation is reached, the hole is lined with pipe called casing, and finally the well is "completed," or made ready for production, with cementing material, tubing, and control valves.

Throughout the rotary drilling process, a stream of fluid called drilling mud is continuously forced to the bottom of the hole, through the bit, and back up to the surface. This special mud, which contains clay and chemicals mixed with water, lubricates the bit and keeps it from getting too hot. The drilling mud carries rock cuttings up out of the hole, clearing the way for the bit and allowing the drilling crew's geologists to study the rock and learn more about the formations underground. The mud also helps prevent cave-ins by shoring up the sides of the hole.

Offshore drilling processes and equipment are essentially the same as those on land, except that special types of rigs are used depending on water depth. Jackup rigs, with legs attached to the ocean floor, are used in shallow water (depths to two hundred feet (61 m)). In depths up to four thousand feet (1200 m), drilling takes place on semisubmersible rigs that float on air-filled legs and are anchored to the bottom. Drillships with very precise navigational instruments are used in deep water (depths to eight thousand feet (2400 m)). Once a promising area has been identified, a huge fixed platform is constructed that can support as many as forty-two offshore wells, along with living quarters for the drilling crew.

Many advancements have been made in oil-drilling technology in the twentieth century. In 1908, American lawyer Howard R. Hughes (1869-1924) and his partner Walter B. Sharp (1860-1912), an American drilling engineer, patented a steel, cone-shaped drill bit with rows of steel teeth. Soon the Hughes cone drill bit was being used worldwide. Through the 1920s numerous innovations were made, including the cross-roller rock bit. Hughes and his scientists also developed the first self-cleaning rock bits and introduced tungsten carbide as a bit facing hardener. Along with other improvements, this hardener resulted in a standard form of drill-bit tooth that has been used nearly continuously since 1926. The most advanced rotary cone rock bits available today can drill about 80% faster than bits from the 1920s. Depths of more than 16,500 feet (5,030 m) have recently been reached through improvements in other drilling support technologies.