Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Sol Greer
Petroleum is the most sought after natural resources. The largest problem most of the world, primarily the United States, faces is the finite resources with the growing demand for oil. while most of the more easily attainable oil has or is being mined, there are still available reserves. The problem lies in reaching these.
Understanding crude oil is the first step in the process. Crude oil comes from hydrocarbons, which are minerals made up of only hydrogen and carbon. These hydrocarbons are remains of organisms, usually zooplankton and algae, and a result of years of exposure to extreme pressure and heat. Typically, the organic remains will flow to a lower elevation such as lake beds and down river mixing with sediments and forming a hydrocarbon rich rock. After many years different layers of clay, silt, and sand settle on top of these remains. As more and more layers continue to build on top of the organic materials, the layers produce the necessary pressure along with the growing depth granting access to heat, for the production of crude oil.
For oil reserves to form, special conditions must be met apart from the hydrocarbons presence. There must be three different layers of rock. First of all, there must be a layer of hydrocarbon rich rock that meets the requirements of heat and pressure to create crude oil. Oil is less dense than both rock and water. Because of this, it naturally raises closer to the surface. There must be a porous layer of rock, such as sandstone, limestone, or dolomite, for the oild to gather and store in. Finally, there needs to be a layer of impermeable rock about the oil to prevent the oil from escaping to the surface. This final layer is typically shale, made of the pressurized, heated clay that covered the layers in the beginning of the entire process.
During the process, oil is formed. However, it is rarely in a state suitable for harvesting. Linear crevasses within the final layer give the oil a path to travel to the highest possible altitude due to its buoyancy. Once oil from a large area gathers in a central location, we can start the drilling process. Unfortunately, not all the old makes it to the reserves. Oil can sometimes take years to reach a point suitable for drilling. Oil remains, in small portions, along the majority of the shale layer. While drilling grants us access to the reserves, the smaller deposits remain untouched.
Fracking is a process in which people can stimulate breaks, typically in the shale layer, which allow faster movement of the natural resources along their path to a reservoir. This is done by pumping fracking mixtures down a well. The well gains pressure and the shale breaks in response to the pressure. The fracking fluid consist primarily of water and sand but also include different chemicals depending on the well and the site. The mixtures of different chemicals are very protected and well monitored.
Cement pipes are first places at the base of a well. As drilling commences, pipes a continually lowered to protect the ground water and soil composition, and to allow the pressure to build up within the well. Once the pipes are lowered into the depth of the well, fracking material is then pumped into the well. As the pressure in the well builds, the small cracks within the shale increases and expand allowing faster flow of oil and natural gases. This way, people can speed up the amount of oil a well is able to produce.
Fracking poses a few problems. First of all, well life expectancy is lowered. Generally speaking, a well that has been fracked usually reaches its life span within two years of drilling. These wells can produce more resources later on in life, but may take up to 50 years to produce enough oil to constitute drilling again. Another much more public concern is the possible contamination of ground water. If the cement pipes are not properly sealed or break, the fracking material could leak into the water table. Perhaps the most attention that fracking receives is the use of the actual fracking matials. In addition to the chemicals, it takes several thousands gallons of water and sand to effectively frack a well. So is this use of other natural resources and possible contamination of ground water worth this? If not, what are we going to do when the natural oil reserves dry up without the use of fracking?