Hydraulic Fracturing: Integration of New Technology and Environmental Effects
Table of Contents
Many countries depend on carbon as a source of energy to drive their economies and natural gas is seen as the most viable option in attaining a lower-carbon energy economy. Projections show that countries such as the United States will become increasingly reliant on natural gas in the future. There has been tremendous growth in natural gas production, in various countries like the United States. These countries have been low producers but may now become net exporters of natural gas in the near future. Hydraulic fracturing, or fracking, is defined as a process by which a fluid – a mix of water, sand, and chemical additives – is injected into wells under high pressure to create cracks and fissures in rock formations that improve the production of these wells. This technology was first developed in the early 20th century but was not commercially exploited until the 1940s. This paper has dealt with the theoretical aspects of the system, new developments and significant advances in technology. It also focuses on the environmental impact of the process as well as concerns raised by various interested groups. This paper focuses on the central innovations involving a combination of hydraulic fracturing, horizontal drilling in shale formations and integrated computer systems for monitoring operations. These innovations have unlocked the potential of natural gas and will surely transform the energy sector. This paper is different from other researches in that it has incorporated the technique itself, environmental concerns and various innovations that are aiding the process.
(Keywords: Hydraulic, fracking, seismic, casing, well, well integrity, environment, natural, underground, bedrock and monitoring)
Natural gas is seen as the most viable option in attaining a lower-carbon energy economy. Many countries depend on carbon as a source of energy to drive their economies and projections show that countries such as the United States will become more reliant on natural gas in the future. For instance in the US, the dramatic increase in domestic shale gas production has led to the growth in natural gas production, it is projected that by 2021, the United States will be a net exporter of natural gas (American Petroleum Institute, 2010).
The process of extracting natural gas out of unconventional sources has been found to be complicated and expensive as compared to conventional natural gas recovery. However, in recent years, the improvement in technology has made extraction from unconventional sources more economically viable (Bamberger &Oswald, 2012). The combination of horizontal drilling and hydraulic fracturing has particularly improved the productivity levels of natural gas sources such as wells. These methods, however, have adverse environmental effects and social impacts especially on other resources important to man such as water resources (Arthur et al, 2008).
The process of exploration, development, and production operations of all oil and natural gas are conducted to ensure that the environment, in particular underground sources of drinking water is protected like the underground water sources (Beauduy, 2011). There are laws that have been put in place to ensure that oil and natural gas operations are conducted in an environmentally compatible manner. Even though these regulations vary from one country or state to another, the general intent and objectives are consistent as far as the environment is concerned.
The resources such as water are normally secured from contamination with the contents of the well during drilling, hydraulic fracturing, and production operations with a combined force of steel casing, cement sheaths as well as other mechanical isolation devices installed as a part of the well construction process (Carrillo, 2005). Impermeable rock structures that lie between the hydrocarbon producing formations and the groundwater have helped in isolating and protecting the groundwater for many years. Well must be constructed properly so as to prevent communication – the migration and/or transport of fluids between these subsurface layers (Fugleberg, 2011).
Hydraulic fracturing, or fracking, is defined as a technique by which a fluid is injected into wells under high pressure to trigger cracks and fissures in rock formations that improve the production of these wells (Cipolla et al, 2010). Fluid is a mixture of water, sand, and chemical additives. Developed in the early 20th century, the technique was not used commercially until mid-to-late 1940s.
It is standard practice for extracting natural gas from unconventional sources, such as coalbeds, shale, and tight sands, and the process is finding an increasing application in conventional sources for productivity improvement. For example, in the United States, the process of hydraulic fracturing is reportedly used on 90% of all oil and gas wells drilled in the country, although the statistics could be higher than estimated (Kargbo et al, 2010).
Although, the technique has been hailed as a game changer, it has attracted controversy in equal measure in many countries. It creates jobs and lower energy prices, but others criticize it for environmental concerns and there have been ardent calls in the past for disbandment of the process in order to protect the environment (Arthur et al, 2008). Hydraulic fracturing has generated a tremendous amount of controversy in recent years.
The debate on hydraulic fracturing has centered on the use of chemicals in the process and concerns that these chemicals could come into contact with drinking water, making it unsafe for consumption. As a result, several countries and states have devised laws and regulations that are aimed at making natural gas operators disclose to the public the chemicals used during well injection. In the United States, a website has been established by the Ground Water Protection Council and the Interstate Oil and Gas Compact Commission which allows companies to voluntarily disclose water and chemical usage for wells since early 2011 that have been hydraulically fractured (Groat & Grimshaw, 2012).
This issue of making gas operators to disclose the chemicals may not be the most important for water resources, but it helps in tracking contamination. There are other major issues about hydraulic fracturing that come into play such as the massive water and the potential conflicts with other water needs, including use in sustaining ecosystems and for agriculture.
There can be methane contamination of drinking water wells, and this raises a lot of concern as it makes the water unfit for human consumption. Furthermore, the process poses a major challenge in the way the waste water should be stored, transported, treated, and disposed (Hammer &Van Briesen, 2012).
There are various methodologies that can be used to execute this process. Down-Hole Process can be used whereby the existing subsurface porosity, or lithologies, Network is fractured artificially by directing a water jet or that of other fluids, under very high pressure. This process requires heavy infrastructure including oil and gas heads equipped for hydraulic fracturing technology to undertake depths of up to 20,000fts (Fugleberg, 2011). Diversity of Proppants are needed which involves fracturing in of pure remedial compound, and 3D modeling of fractures. This is normally applicable in more difficult geology. The most widely used proppant is sand, but there are others such as isolite, resin-coated silica beads, zero-valent iron, chitin, and solid oxidants like permanganate.
These include storage tanks, proppant transport equipment, pumping equipment, blending equipment and all ancillary equipment such as hoses, piping, valves, and manifolds. Data needs to be collected from the various units, and sent to monitoring equipment. The data include fluid rate from the storage tanks, slurry rate being delivered to the high-pressure pumps, wellhead treatment pressure, the density of the slurry, sand concentration, chemical rate and many more. Therefore, appropriate measuring equipment will be required (Canadian Society for Unconventional Gas, 2010).
Hydraulic fracturing technique has been in use for some time now, but recent innovations on the technology sector have seen integration of computer technology in the process especially in the monitoring of fracture elements and location of microseismic events. It is imperative that the fracture treatment is monitored and controlled during the process. The pumping rates and pressures of the fracture fluids are controlled by specialists using special management systems (CSUG, 2010).
Pump tests usually done source aquifers can be done using pressure transducers like the YSI Level Scout. The information obtained from the test is used to establish aquifer’s characteristics and establish whether or not large amounts of water pumped will negatively affect nearby residential, wells or local stream flow in the municipality. There are other innovative techniques that are used to during the hydraulic fracturing operation to help in determining the degree of success of the treatment. These include sophisticated systems for testing of isolated intervals in the wells during the flow back, and observation of extremely small seismic movements when fractures are created (CSUG, 2010). A special modeling system is now available that can be used to locate those micro-seismic events by plotting in 3D space that allows the configuration of the fracture treatment to be observed.
In order to protect the underground water, extreme care must be taken during the drilling operations. The process involves drilling the well bore through the groundwater aquifers, installing a steel pipe casing immediately and cementing this steel pipe into place. There are regulations in place that govern groundwater protection, including requirements for the surface casing to be placed below the lowest groundwater aquifer (Schueler, 1994).
During subsequent drilling operations, the steel casing protects the zones from material inside the well bore. Furthermore, protects the groundwater with multiple layers of protection for the life of the well in combination with other steel casing and cement sheaths that are subsequently installed (Hammer &Van Briesen, 2012).
In this process, the subsurface zone or structure containing hydrocarbons finds their way into the wall, and that production is sustained in the wall and all the way to the surface. This phenomenon of containment and sustainment is referred to as well integrity. Protecting the water sources and the environment in general demands regular monitoring during drilling and production operations so that operations proceed as per the established parameters and in accordance with the well design, well plan, and permit requirements (Zoback, Kitaseib, &Copithorne, 2010). Periodical testing is also done to ensure that its integrity is maintained, and the monitoring activities are normally done prior to and during the construction and over the life of the well (Zoback, Kitaseib & Copithorne, 2010).
There are three monitoring methods in use currently, and they lead to a better understanding of the hydraulic fracturing process (Urbancic &Trifu, 2000). The first one is micro-seismic monitoring which depicts the spatial distribution and the scale of seismicity associated with bedding plane slip as well as slip of natural and incipient fractures. The limits of the dilated zone are thought to be contiguous with the region of detectable micro-seismicity (Wiles & MacDonald, 1988).
The second one is deformation monitoring which uses tilt-meters to allow decomposition of the fracturing process into vertical and horizontal components and provides insights into shape and magnitude of the stimulated zone. Finally, there is the pressure measurement which is done during and after hydraulic fracturing process to allow insight into the process, estimate permeability, and open volume generated (Barrie, Barrie &Craig, 2009). Things like post-treatment pressure tests can also be done, and this involves pulses, build-up and decay together with sophisticated methods of analysis which provide an insight into the scope of the stimulated zone, its deformity, and the flow properties (Dusseault & Simmons, 1982).
Real time implementation of all three monitoring approaches is achievable and fundamentally used to track and optimize treatments. More often it requires rapid analysis methods, excellent graphic capability, and a strong conceptual model of the mechanisms involved. A combination of analysis methodologies used in data collected provides a much better understanding of the size of the stimulated volume and its flow properties as discussed above (Bray &Goodman, 1981).
The process of drilling a typical oil or gas well involves several cycles of drilling, running casing which is a steel pipe for well construction as well as cementing the casing in place to ensure isolation. A steel casing is installed in each cycle as sequentially smaller sizes in the previous installed casing string. The last part of well construction is well completion process which involves the perforation and hydraulic fracturing (Damjanac et al, 2010). The drilling process makes use of the drill string, consisting of drill bit, drill collars and the drill pipe. The process begins with the drill string being assembled and run into the hole but suspended at the surface from the drilling derrick or mast. Next is to rotate the drill string using a turntable (rotary table), top drive unit, or down-hole motor drive (Ladanyi & Archambault, 1970).
As the drilling process continues, fluid is circulated down the drill string and up the space between the drill string and the hole ((Damjanac et al, 2010). The purpose of this drilling fluid is lubrication of the drilling assembly, removal of the formation cuttings drilled, to maintain pressure control of the well, and stabilization of the hole being drilled. The composition of the drilling fluid is usually a mixture of water, clays, fluid loss control additives, density control additives, and viscosifiers.
Analyses show that there is an increasing production in natural gas currently, and that is likely to be the trend for the next three decades. The supply is expected to be largely from unconventional sources, especially shale gas. These sources have come to be more economically viable in recent years as opposed to earlier when it was very costly to adopt. This is due to the application of horizontal drilling and hydraulic fracturing techniques in the mining of the gas. These technological advancements have contributed to the rapid development of the natural gas both in areas with pre-existing natural gas operations and new ones. Although it has contributed a lot in a positive way, the technique has attracted criticism in equal measure because of environmental concerns.
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