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Hydraulic fracturing, also known as fracking, is an innovative and rapidly developing technology in the petroleum industry. It is gaining popularity over traditional extraction technologies since it has introduced horizontal drilling techniques which allows reaching previously inaccessible rock formations that are tapped for hydrocarbons. Hydraulic fracturing is highly complex, and the industry continues to face a myriad of challenges in its implementation and environmental safety. The purpose of this report is to investigate the development of water treatment technologies which maintains a vital role in the process and waste of the fracking process. It is aimed at a general audience with a basic understanding of petroleum engineering, seeking to learn information on the complexities of the fracking process.
Basics of Fracking
There has been a significant increase in the natural gas production in the U.S. recently (Haluszczak, Rose, and Kump 2013). This occurred due to increased use of hydraulic fracturing of natural gas from inaccessible shale formations. Hydraulic fracking is an extraction process which consists of injecting water, mixed with sand and specialized chemicals, into wells. Fracking is used for both, oil and natural gas. As the fluid is injected, there is an increased resistance to flow, causing a rise in the wellbore pressure to a value known as “break-down pressure” (Chen et al. 2014). It eventually exceeds the sum of compressive stress and strength of the shale formation. Once extremely high pressure is created, a fracture begins to open and cracks pores in the shale formation, releasing hydrocarbons as the injecting fluid flows. The fracture is widened gradually until there is enough space to fit a propping agent, which consists of corrosive resistant sand or ceramic beads meant to maintain the opening. In combination with technological advances, hydraulic fracturing is a highly innovative method to reach difficult to reach reserves of oil and gas, such as those located in shale formations. Horizontal drilling has allowed for a wider application of fracking in the last decade, creating a debate over the viability of such methods.
Water Composition and Environmental Impact
When the water is pumped into the well for pore creation, it eventually flows back and collected. However, this water contains a concentration of chemicals, heavy metals, salts, oil greases, and a combination of volatile and semi-volatile soluble organics. Other substances which may be present in the water composition include reducing polymers, corrosion and scale inhibitors, and biocides. Chloride levels increased from 82 mg/L to 98,000 mg/L in 14 days after drilling (Haluszczak et al. 2013). Furthermore, levels of radium and barium, naturally occurring radioactive materials, significantly exceeded drinking water regulation set by the Environmental Protection Agency (Haluszczak et al. 2013). All of these are inherent for drilling operations as they reduce any issues with the process. However, there is extensive environmental contamination as a result, leaving the water unusable for any other purposes.
As noted, fracking creates concerns and have been linked to environmental impacts. First, there is a significant risk of groundwater and drinking water contamination, particularly if fracking occurs nearby. There are high-density gas emissions commonly recorded near fracking wells. The impact that fracking has on shale and soil along with horizontal drilling can induce seismic activity and earthquakes in the area (Meng and Ashby 2014). Furthermore, it impacts the local ecology and landscaping characteristics. Finally, it presents an increased risk to human populations due to health concerns from emissions and contaminations (Meng and Ashby 2014).
Water volume and composition is an issue as well. Fracking requires significant amounts of water of approximately 4 to 6 million gallons to stimulate a contemporary unconventional well (Chen et al. 2014). Water is collected from ground and surface sources alike, which limits the availability of the liquid to be used for other purposes in the area. Water management is costly and leaves a tremendous ecological footprint as part of the fracking process. In addition, without a system of waste treatment in place, the water could contaminate nearby areas leading to health issues and casualties. Therefore, water management has become synonymous with hydraulic fracking as a technology that presents technical and economic challenges. The industry is under public and government pressure to consider technological innovations which will aid with environmental stewardship.
Freshwater supply is becoming increasingly difficult and more expensive to obtain for hydraulic fracturing purposes. In several states, regulation has been put in place to manage water acquisition. This occurred due to exuberant amounts of water being taken from natural sources, leading to limited amounts left for farming or drinking use. In areas such as the Missouri River watershed, the Army Corps of Engineers prohibited the acquisition of water from the river. A series of hydraulic fracturing wells may use four to eight million gallons of water in a period of one week, and up to 6 billion annually for just one formation (Haluszczak et al. 2013). Some wells may be fractured numerous times over a productive life of up to twenty years. Therefore, the growing value of water supply and strict regulation are causing hydraulic fracturing operations to consider options in wastewater management.
Half of the water used in the fracking process is recovered as “flowback.” It contains high concentrations of chemicals and brine and is, therefore, both challenging and costly to treat (Haluszczak et al. 2013). A common practice is to inject the water deep underground. These deep wells are usually old drained oil or gas sites and there is no need for sophisticated treatment. However, recent regulation has banned this common practice in many jurisdictions, causing operators to consider treatment and recycling option for flowback water (Bolte 2017). Currently, the use of flowback water is rather low but is expected to increase due to regulation and freshwater costs (Smith, Van de Ven, and Richardson 2017). If appropriate technology is developed, it will significantly reduce costs of transportation for operators.
Commonly, without the availability of deep-oil wells, companies will consider reusing flow water. It is filtered for metals, hardness, and bacteria counts and blended with fresh water to be used at another site. Each drilling company maintains its unique specifications, but the dilute rate can be 20:1, leaving a very low percentage of flowback water. Wastewater can be used until it exceeds a specific limit (Haluszczak et al. 2013). Various technologies and innovations have been utilized for management of fracking wastewater. There is the process of oxidation, using chemicals to eliminate organic compounds. Reverse osmosis is possible as by cleaning the water through a membrane filter. They are partially utilized in freshwater municipal systems, and greater exposure to the knowledge of these proven technologies can lead to a better adoption rate.
Centralized vs. Modular Treatment Systems
A centralized approach to water management seeks to optimize utilization of water resources while combining the aspects of treatment and recycling of wastewater. Centralization seeks to provide treatment to a large number of wellheads at the initial stages and throughout the operating lifecycle of the well. A centralized system allows easier access and provides alternative sources of water such as municipal facilities. Shale formation development through fracking is a long-term process, but most water management solutions are geared towards short-term operations (Chen et al. 2014). The benefits that a centralized system can bring has led to wider adoption in the United States.
One of the strongest aspects of wastewater management offered by a centralized system is that it can offer solutions to recycling and reuse of flowback wastewater. It eliminates the need for off-site transportation or mobile filtration systems which are less effective. A centralized system can offer viable and long-term processible of fracking wastewater. The treatment facilities can collect both flowback and produced wastewater from any oil or gas well within a range of 50 miles, directly through pipeline transportation (Bolte 2017).
Once the wastewater is received, it is identified as being from a specific location. The target usage specifications and requirements of the drilling company are confirmed. The wastewater is processed accordingly and piped directly back to the well site. As a rule, centralized wastewater management offers a broader scope of filtration and treatment options (Chen et al. 2014). These include multi-stage separation to remove chemicals and suspended solids (Smith et al. 2017). Reverse osmosis is used to remove heavy metals, whereas dissolved air flotation can be used to remove over contaminants and bactericide eliminates organic compounds (Chen et al. 2014). Overall, centralized systems are more permanent and can be easily integrated with both water sources and locations for water disposal after it becomes unusable.
A modular water management approach is a mobile, portable water treatment and sewage system which can modify its network with additional treatment units. The units can be added and removed in order to match the requirements of the drilling company, to scale the system in accordance with water treatment needs. This provides flexibility and cost efficiency (Haluszczak et al. 2013). The main benefit of modular systems is their portability, as they can be delivered in shipping containers in virtually any location globally. As a result, modular systems become attractive for remote locations, particularly from an environmental standpoint due to a low ecological footprint. Furthermore, the technology is efficient, easy to implement, and redeployable, maintaining low capital and operating costs.
Modular technology can be adapted for different variations of processes, treating wastewater in either batches or a continuous cycle. Most modern modular systems utilize a combination of a chemical filtration system and a membrane biological reactor (Bolte 2017). These reactors use various technologies for filtration. High-pressure membranes are used for reverse osmosis and nanofiltration. Additionally, novel membranes are helpful in forward osmosis and membrane distillation (Haluszczak et al. 2013). There are also electric processes such as CDI and electrodialysis. Thermal technologies use vapor compression, multi-stage flash, distillation. It can also be adapted for evaporation and crystallization (Botte 2017).
In response to the water management problems discussed earlier, the petroleum industry is actively seeking methods to mitigate the issues surrounding hydraulic fracturing. Treatment and reuse of water is not just a matter of technological capabilities, but also a reform of logistics and economics with the tools to improve water management (Smith et al. 2017). Moreover, the significant water needs and the drilling process during fracking is requiring varying flow rates and amounts necessary. Therefore, water infrastructure should be adequately developed and strategically implemented to account for the operating life of a well.
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Generally, water is transported via road by trucks, especially for short to medium distances. However, due to limited volumes of water that a truck can carry, it may require over 1000 trips to the well in its initial stages (Smith, Van De Ven and Richardson 2017). This leads to environmental concerns such as pollution, congestion, and vehicle accidents. This makes reuse of flowback water more appealing. Furthermore, operators have developed temporary conveyance systems which use lay flat hoses as a cost-effective option for transportation of water rather than permanent installations that present their own challenges. In addition, storage of water is another critical aspect, especially in situations where pipeline networks are not available (Botte 2017). Selection of water storage is dependent on capacity, ecological footprint, and regulatory specifications. Most commonly ponds, pits, and storage tanks are used.
As far as the economic perspective on water management is concerned, it is vital for fracking development and allows to understand the value of water. The costs of water management and logistics described above are rarely investigated and quantified for producing regions (Meng and Ashby 2014). Since wastewater management is often dependent on local factors such as disposal options, state regulations, and availability of freshwater basins which all impact storage, treatment, transportation, and infrastructure, they are neglected in water-cost calculations (Botte 2017). Sometimes, the cost of obtaining, cleaning, storing, and disposing of water in hydraulic fracking can reach up to 30% of total operational costs (Smith et al. 2017). If drilling companies and the public were more aware of these significant costs and logistical issues of water delivery, it could lead to reforms for the reuse of water on site.
Hydraulic fracturing is an extremely controversial aspect that has mixed perspectives. While some welcome the energy boom it may encompass for the United States, others view the significant ecological dangers it poses. For one of the leading experts in the area, Mark Zoback, fracking is an innovative field, but it requires significant investment in technology and regulation (Smith et al. 2017). Regarding regulation, there should be both state and federal levels of enforcement. As a rule, the Environmental Protection Agency commonly governs injection wells and major aspects of oil and gas development (Smith et al. 2017). However, states need to do more to regulate their respective public and environment. State legislation should develop specific plans for water use and road or pipeline networks. Those states that approach the topic conscientiously usually have the most success with fracking in terms of balancing economic and ecological footprint (Smith et al. 2017).
Water is a critical resource in many places around the world, including some regions of the United States as more states, experience drought each year (Meng and Ashby 2014) Therefore, fracking may not be commercially viable with the water sourcing risks. The rapid development of hydraulic fracking has caused the public, government regulations, and water management technologies largely underdeveloped (Bolte 2017). Therefore, regions, where water sources are limited but have seen an increase in fracking, have seen growing competition for limited groundwater. Thus, the industry should communicate with the public and governments to ensure there is a strategic plan in place for water usage and to avoid crisis situations, for both the population and the fracking wells which may require water (Meng and Ashby 2014).
Drilling operators face a wide variety of water management challenges when using unconventional oil and gas development such as fracking. Water quantities, storage, transportation, characterization, and treatment all require significant innovation. However, effective management and treatment are essential for successful shale fracking operations. Since large amounts of adequate quality water are required on site to avoid disruptions, it is vital for operators to invest in water planning and procuring. Furthermore, environmental concerns and social pressures, as well as regulatory limitations, are influencing the logistics and economics of freshwater use. In response, there has been significant technological breakthroughs in the reuse and recycling of water treatment and infrastructure that will minimize dependence on freshwater sources and improve handling of flowback wastewater.
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