Drilling For Oil in Saudi Arabia
- Pipeline
- In Search Of Oil
- Other - In Search Of Oil
Author: Public Relations Department, Arabian American Oil
Released 26 June 2007
Drilling a well is like making a lengthy trip, straight down, into the long ago – millions of years ago – with one goal in mind: to find a dome-shaped formation of porous rock which, like a sponge, may serve as a reservoir for oil.
It takes a powerful drilling rig to make that trip. In the United States the rig is often pieced together at the drilling site like an Erector set. But in Saudi Arabia the Arabian American Oil Company rolls its 400-ton rigs into place on multiple sets of wheels. In that desert land, Aramco does not have to worry about crossing rivers or bridges.
The rig consists of four main parts: derrick, engines, drawworks and mud system. The derrick, 136 feet high, serves as the broad shoulders of the rig. From it hangs a heavy string of drill pipe (the term “derrick” comes from a London hangman of the seventeenth century). The diesel engines are the muscles. They turn the drill pipe and drilling bit that bore deep into the earth. The drawworks is the nerve center. The mud system is the circulatory system.
Aramco’s drilling crews today consist entirely of highly trained Saudi Arabs supervised by an American drilling foreman. Three shifts work around the clock to drill each well. Aramco’s average well in a proven area takes about 35 days to drill and finds oil at from 5,000 to 7,000 feet – roughly four times the height of the Empire State Building. The deepest yet took two years to drill, cost $5,000,000 and reached a depth of 14,875 feet, or almost three miles. It found no oil and was abandoned as a “dry hole.”
THE DRILLING FLOOR is a platform at the bottom of the derrick where the “roughnecks” of the drilling crew work in their hard safety hats. In the center is the rotary table which rotates the drill pipe and bit, like a carpenter’s drill, as fast as 200 revolutions per minute. New 30-foot lengths of drill pipe, weighing about 500 pounds each, are screwed on as the hole is deepened.
SEVERAL TYPES OF BITS are used to chew their way deep into the earth. Sometimes the rock is so hard that the hole can be deepened only one inch an hour. Some rock formations are soft enough to permit a speed of 400 feet an hour. Because of wear and tear, 60 or 70 individual bits may be used to drill one hole. A special hollow bit, studded with diamonds, is used to cut cylindrical cores of rock for geological examination. Such cores, as well as the cutting brought up by the mud system, may provide telltale clues to the presence of oil.
AFTER THE WELL HAS BEEN DRILLED down to an oil-bearing rock, the well bore is lined with a thin-skinned steel casing, cemented in place, to withstand the powerful pressures exerted by the crude oil and dissolved gas. Next comes the job of perforating the well. Explosive charges – sometimes as many as 120 bullets – are set off at the bottom of the well. They puncture the steel and cement casing in order to let the oil flow. In addition, the well may be washed with hydrochloric acid to dissolve the mud cake and to open up the pores in a limestone reservoir. Then a many-branched trunk of pipes and valves, called a “Christmas Tree,” is installed over the mouth of the well. Finally, natural pressures force the crude oil, like soda water in a siphon bottle, to the surface at a rate controlled by the Christmas Tree. Once the well is brought in, the drilling rig is wheeled away to another site, leaving only the Christmas Tree visible as a year-round ornament.
THE LONELIEST JOB on a drilling rig belongs to the derrickman. Strapped by a safety belt to the “monkey board” high up in the tower, the derrickman attaches the elevators to the drill pipe each time a new section is added. By the time the drill pipe stretches to 6,000 feet, it consists of 200 lengths of 30 feet each and weighs about 50 tons. Whenever a worn bit has to be changed, the drill pipe must be lifted from the hole and unscrewed into 90-foot “strands,” which the derrickman stacks inside the rig. After the bit has been changed, the pipes of the drilling string are screwed together again. More time is often spent on these “round-trips” than in actual drilling.
TENS OF THOUSANDS of gallons of water are needed each day for drilling an oil well, especially for mixing mud. The best way to find water in the deserts of Saudi Arabia is to drill for it. Once water has been discovered, the well site becomes a man-made oasis, with watering troughs provided for camel herds.
THE DIAGRAM IDENTIFIES some key parts of a drilling rig. The draw-works, with its geared winches, transfers the engines’ power to the rotary table, as well as hoisting the drill pipe by means of a block-and-tackle system of huge pulleys and thick steel cable. While the rotary table revolves the drill pipe and bit, the mud system circulates a mixture of water, clay and chemicals (called “mud” by oilmen) through the hollow drill pipe out through holes in the bit, and back to the surface. This mud cleans, cools and lubricates the bit and removes the rock cuttings. It helps control any high-pressure flow of oil or gas. It also deposits a mud pack (like a lady’s facial) on the walls of the well to prevent cave-ins.