Hydraulic fracturing is a process within the mining and drilling industries used to increase the output of an underground fluid. Fracturing is used to access or augment productivity in petroleum, water and natural gas. The actual process is accomplished deep underground when a pressurized fluid is ejected from underground piping into the surrounding rock formations. The pressure of the fluid creates a crack in the rock which continues to expand as the pressure is applied. Solid additives in the pressurized fluid prevent the rupture from resealing once the pressure is alleviated. Sand and ceramics are commonly used as additives because their porous nature also allows the desired resource to travel to the piping. The increase in the size and number of underground networks due to the fracturing allows greater fluid output. In some instances the retrieval of an underground fluid would not be possible without the use of hydraulic fracturing. Shale reserves, located about 5,000 feet underground, suffer an exceptionally low permeability rate. Permeability is the measure of how well a fluid flows through a porous material. At that depth, and within such nonporous rock, the ability of fluids to travel to the well is greatly limited. Fracturing increases the area of the fluid that is exposed to porous materials and thus greatly increases production. The method of fracturing utilizes a few key components which allow for an economical extraction of resources.
The fracturing process applied in a horizontal well through shale. Simplified Steps in Fracking (n.d) Retrieved from: http://www.hydraulicfracturing.com/Process/Pages/information.aspx
Components of Hydraulic Fracturing
The entire fracturing operation takes places near the well site that connects the underground resource. The drill hole turns horizontal once it reaches the depth of the resource so as to increase the area of the well exposed to the resource. A steel or cemented casing surrounds the underground piping to prevent chemical leaks into surrounding rock or water wells. The main components used for the fracturing process are located on the surface near
the drill hole. Large quantities of water, sand and chemical additives are stored near the well for use as the fracturing blend. A monitoring station tracks the process of the fracturing by analyzing data from geophones. A geophone is a device that converts ground movement into voltage that can be transmitted to a recording station. A “frac” blender near the well is used to mix all the ingredients of the fluid that will be ejected down the well. Large pumps are required to create and maintain the fluid pressure that must travel thousands of feet underground and operate for long periods of time. Fracturing pumps must be capable of producing 5,000 to 10,000 pounds per square inch of pressure at the ejection site. Depending on the size and width of the well a pump can eject 200 liters of frac per second. Once the desired amount of rock fracturing has occurred the fluid is withdrawn up the well while the sand and additives remain holding the rupture open. The entire process is relatively simple and straightforward. The main area available for specialization is the mixture of the fracturing fluid. The fluid is roughly ninety eight percent water and sand; however the remaining solution is composed of chemicals which serve specific purposes. Some commonly used additives in the fracturing mixture include: acid, anti-bacterial agent, breaker, clay stabilizer, corrosion inhibitor, friction reducer, gelling agent, iron control and pH adjusting agent. These components are used to prevent corrosion on the piping, assist in the breakup of rock and reduce friction on the fluid. The concentration, volume and toxicity of said ingredients have created concerns over the safety of hydraulic fracturing. Environmental and Health Concerns:
The effects of hydraulic fracturing on the purity of groundwater have concerned health officials and environmentalists alike. The concerns are based on the possibility that gas and chemicals from drilling operations are leaking into groundwater supplies. These concerns seem to be validated in a 2011 Duke University study which found methane levels 17 times higher in private water wells that were within 1,000 yards of a drilling operation. A similar study by the EPA in 2010 found heavy metal contaminants, which can cause severe illnesses, in drinking water near drilling operations. Other fears over the safety of hydraulic fracturing are based on the potential for the underground actions to create seismic disturbances. The United States
Geological Survey has reported that fluid injected into deep wells can cause earthquakes. In 1967 a 5.5 magnitude earthquake recorded in Colorado was allegedly caused by a series of fluid injection operations. The process of hydraulic fracturing has been plagued by unsafe health practices since its origination. History of Application
Some of the earliest evidence of hydraulic fracturing comes from the oil wells of Pennsylvania near the end of the 19th century. It was developed as a method of increasing the productivity of oil wells similar to modern procedure. However the propellant agent used then was a much more hazardous chemical called nitroglycerin. The pressurized NG (nitroglycerin) was used to break up underground obstacles and thus increase the oil output. The same principle was soon applied to water and gas wells. By the 1930s a transition to a non explosive propellant was used in most fracturing operations. Today the pressurized fluid ejected down hole is almost wholly sand and water. A few additives are also applied to maintain the rupture size and assist the transport to the piping. The ubiquity of hydraulic fracturing has increased stupendously since its first applications. It is estimated that up to ninety percent of gas wells drilled today utilize hydraulic fracturing.
Bauers, S. (2011, May 19). Duke Study Finds Methane Gas Near Well Water Sites. The Philadelphia Inquirer. Retrieved from http://www.philly.com/philly/news/121515559.html?c=r Fracturing Ingredients (n.d.) Retrieved from http://www.hydraulicfracturing.com/Fracturing-Ingredients/Pages/information.aspx Montgomery, C.T. & Smith, M.B. (2010). Hydraulic Fracturing: History of an Enduring Technology. Journal of Petroleum Technology. Retrieved from http://frack.mixplex.com/content/hydraulic-fracturing-history-enduring-technology New York Department of Environmental Conservation. (2010). Materials and Minerals. In Natural Gas Development Activities and High Volume Hydraulic Fracturing. Retrieved from: http://www.dec.ny.gov/docs/materials_minerals_pdf/ogdsgeischap5.pdf United States Geological Survey. (2009). Earthquakes, Faults, Plate Tectonics, Earth Structure. In Can We Cause Earthquakes?. Retrieved from
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