It wouldn’t be surprising if many people thought that drilling for oil was as simple as inserting a straw into the plastic top on a glass of soda.
The cut-away diagrams shown on TV seem almost as simple.
The reality is much different. The technologies are varied and incredible.
We have come a long way since Drake’s Folly, where drilling merely consisted of repeatedly dropping a pointed weight into the well to wear away the rock until oil was found.
Percussive drilling was replaced by rotary drilling, which was the new technology at the turn of the twentieth century.
The evolution of rotary drill bits, from those that work in sandstone to those with carbide tipped cones that work on hard rock, with mud forced through the drill bit to cool the bit and clear debris, together with the rotary drilling table, were the first attempts at developing new, scientifically based technologies.
What has evolved is truly incredible.
On land, consider directional or horizontal drilling. After drilling through rocks of varying hardness, it requires bending the “straw” at the correct depth in the right direction until it reaches the desired plane, and then continuing to drill horizontally for at least a mile. All of this is accomplished out-of-sight using instruments.
Then there is deep water drilling in the ocean, at depths of over 5,000 feet.
The Cascade and Chinook wells were drilled at 8,000 feet below the surface.
Moored to a buoy at these wells, a ship will process the crude as it is brought from the well. The ship, a floating production, storage, and offloading vessel (FPSO) is moored to a special double hulled buoy so the ship can rotate around the buoy and always face into the wind.
The FPSO ship can be disengaged from the buoy in the event of a hurricane, and the buoy can be automatically lowered to 150 feet below the surface so as not to be affected by the wave motion caused by hurricanes.
Pipes within pipes are laid on the ocean floor between the manifolds and trees. The outer pipe is 14 inches in diameter, while the inner pipe is 9 inches in diameter. Joining these pipes requires an understanding of the differing tensile strengths and coefficients of expansion. Barriers are also welded between the inner and outer pipe to create chambers to catch any oil that might leak from the inner pipe.
The outer pipe has to have “strakes” or fins mounted in a spiral form on the outside of the pipe to prevent high-speed tidal currents from creating vibrations that can damage the pipe and other equipment.
The oil and gas are brought to the surface through free-standing risers that connect the wells to the buoy, which in turn is connected to the FPSO ship.
The risers are 9 inches in diameter with wall thicknesses of over an inch, containing oil and gas under high pressure, perhaps 10,000 psi. Attached to each riser is a “can” filled with nitrogen to help support the riser. These buoyancy cans are 120 feet long, which is the height of a ten-story building, and 21 feet in diameter.
The weight of the oil in the riser creates sufficient pressure at the wellhead, 8,000 feet below the surface, to slow or stop the flow of oil from the well.
To ensure the proper flow of oil up the risers and to the FPSO, electrically-powered booster pumps, connected to the risers, are laid on the ocean floor to assist the natural flow of oil caused by pressure within the well.
All of this equipment must be built to withstand the underwater pressure at 8,000 feet below the surface. Lines containing oil and gas must be insulated to prevent hydrates from forming if flow stops for more than a few hours.
Every well is different, so different solutions are found to the many problems encountered while drilling.
The engineering and science needed to support drilling is remarkable. Seeing the equipment, especially that which is used in deep water drilling, is breathtaking.
This is an industry in which the United States is a leader. It’s an industry that can support the re-industrialization of America, strengthening our economy with a concomitant increase in jobs.
Read more of Donn’s columns at his blog, Power For USA.
© Power For USA, 2010 – 2012
Our nation must drill for oil!