Environmental Science 15th Edition by Scott Spoolman,Tyler Miller

Exercise 18

REMOVING TIGHTLY HELD OIL AND NATURAL GAS BY DRILLING SIDEWAYS AND FRACKING
Geologists have known for decades about vast deposits of oil and natural gas that are widely dispersed and trapped between compressed layers of shale rock formations found deep underground in many areas of the United States, including North Dakota, Texas, and Pennsylvania.
Until recently, it cost too much to extract such oil (called tight oil ) and natural gas from shale rock. This situation has changed because of high oil prices along with the growing use of two extraction technologies (Figure 13.A). One is horizontal drilling , a method that involves drilling first vertically to a certain point, then turning the flexible shaft of the drill and drilling horizontally to gain access to the tightly held oil and natural gas deposits.
The second technology, called hydraulic fracturing or fracking , is then used to free this trapped oil and natural gas. In a fracking operation, high-pressure pumps blast a huge volume of a slimy mixture of water, sand, and various chemicals into a well to fracture the porous rock and create cracks. The sand becomes wedged in the cracks and keeps them open to allow the oil or natural gas and about half the water-chemical mixture to flow out and be pumped to the surface. This hazardous slurry contains a mix of naturally occurring salts, toxic heavy metals, and radioactive materialsleached from the rock, along with some potentially harmful drilling chemicals that natural gas companies are not required to identify or publicize. After fracking, the hazardous wastewater is injected into deep underground hazardous waste wells, stored in holding ponds, or cleaned up and reused in the fracking process.
Each day, energy companies drill and frack about 100 new oil or natural gas wells in parts of the United States. They drill a well, frack it several times, and then drill a new well and repeat the process. The growing use of these extraction technologies has brought about what some experts are calling a new era of oil and natural gas production in the United States. But such production also results in a lower net energy yield, compared to conventional oil and natural gas production, which means that market prices of oil and natural gas must remain high enough to make it profitable to produce oil and natural gas from these deposits.
Critical Thinking
Why do you think horizontal drilling allows better access to tightly held oil and natural gas deposits than does drilling vertically into such deposits?