The Ohios Oil And Natural Gas Industry

Published Date: 02 Nov 2017

â…  Background of oil and natural gas industry in Ohio

A brief history of Ohio’s oil and natural gas industry

The Ohio oil and natural gas industry has a long history that dates back to the 19th century. In the 1860s, the first well drilled in Ohio for commercial production of oil was found in Macksburg, Washington County. Since that time, the Ohio oil and natural gas industry has experienced a rapid development, making Ohio one of the leading producers of oil and natural gas in the nation. From 1888 to 2011, more than 260,000 wells have been drilled in Ohio. Now, Ohio ranks 4th nationally in the number of wells drilled, following Texas, Oklahoma and Pennsylvania (2011 ODNR review). As of February 2012, 460 oil and natural gas wells were drilled in 42 of Ohio’s 88 counties. In 2011, Ohio’s total crude oil and natural gas production was 4,852,964 barrels and 73,289,838 thousand cubic feet (mcf), respectively. The market value for the combined Ohio’s oil and natural gas industry was over 474 million dollars. (2011 ODNR review)

In general, most of the wells drilled in Ohio were located in the eastern part of the state. (Ohio oil and natural gas maps, 2004) In 2011, the average well depth was 4335 feet, an increase of 310 feet from last year. The most active drilling zone in Ohio was the Clinton sandstone. An approximated 215 wells were drilled in the Clinton sandstone, accounting for 47% of all the wells drilled in 2011. (2011 Ohio oil and natural gas summary) According to a report published by the U.S. Energy Information Administration, the proved natural gas and crude oil reserves in Ohio were 896 billion cubic feet and 38 million barrels of 42 U.S. gallons by the end of 2009, making up 0.32% and 0.18% of the total proved natural gas and crude oil reserves in the United States. (EIA U.S. oil and gas proved reserves 2010) Ohio will continue to play an essential role in the U.S. oil and natural gas industry to satisfy the rapidly increasing demand for energy in the future.

Conventional and unconventional reservoirs

Conventional gas

Traditionally, oil and natural gas resources are divided into two different types: conventional gas and unconventional gas. Conventional natural gas is traditionally referred to gas that is reserved in the relatively more porous and permeable naturally occurring rock formations, such as sandstones, carbonates and siltstones. Conventional gas is usually in small volumes that are easy to exploit. Since the beginning of the oil and natural gas exploration, conventional reservoirs have been the major sources of this industry. However, the growth in demand for energy never stops. From 1980 to 2007, the overall primary energy consumption in the United States increased about 30%. (EIA 2011 Annual energy review) In the Annual Energy Outlook 2012 report, it is estimated that the total U.S. energy demand will increase at an average rate of 0.3 percent from 2010 to 2035. (AEO 2012 EIA) As such, the oil and natural gas industry will need to produce more oil and natural gas to meet the demand in the coming years. Unconventional gas has been catching more and more attention due to its large reserves and the development of horizontal hydraulic fracturing technique.

Unconventional gas

Unconventional natural gas usually has large volume but low permeability that was considered impossible to be exploited commercially. (Harper 2008, Holditch 2003) Recently, with the development of drilling technique, especially the application of horizontal hydraulic fracturing technique, the extraction of natural gas from unconventional energy gas plays, such as coal bed, tight sands and shale reservoirs, has been playing a more important role in the supply of natural gas across the country. From 1998 to 2007, the unconventional gas production has increased 65%. In 2007, the unconventional gas production has accounted for nearly half of all the U.S. natural gas production. (Modern shale gas) In the U.S. Annual Energy Outlook 2008, it was reported that lower 48 onshore states’ total unconventional natural gas production would reach 9.5 trillion cubic feet in 2030 from 8.5 trillion cubic feet in 2006, while conventional gas production of the lower 48 states would fall by a third, from 6.6trillion cubic feet in 2006 to 4.4 trillion cubic feet in 2030. (AEO 2008) That is to say, the unconventional natural gas production will become a larger portion of the U.S. total natural gas production in the coming years.

Shale gas

Among the different types of unconventional natural gas, natural gas extracted from shale gas formations has gained more attention and contributed to this dramatic increase of unconventional gas production, owing to the abundant shale gas reservoirs in the United States. As of year-end 2010, the proved shale gas reserves in the United States were 97.4 trillion cubic feet, accounting for 31% of the total U.S. proved natural gas reserves. (EIA U.S. oil and gas proved reserves 2010) In 2011, natural gas provided 26% of all the U.S. primary energy demand, the number is supposed to be up to 28% in 2040. (AEO 2013 early release) However, the large-scale commercial shale gas production in the United States did not occur until late 20th century. The experiment conducted by the Mitchell Energy and Development Corporation during the 1980s and 1990s successfully made the commercial shale gas and oil exploitation come true in the Barnett Shale in Texas. As the success of Barnett Shale, shale gas production has expanded all across the country. Currently, the shale gas plays in the lower 48 states include Bakken shale in the Williston Basin, Mowry shale in the Powder River Basin, Niobrara shale in the Denver Basin, Barnett-Woodford shale in the Permian Basin, Barnett shale in the FT. Worth Basin, Woodford shale in the Anadarko Basin, Eagle Ford shale in the Western Gulf, Haynesville-Bossier shale in the TX-LA-MS Salt Basin, Fayetteville shale in the Arkoma basin, New Albany shale in the Illinois Basin, Antrim shale in the Michigan Basin, Devonian, Marcellus and Utica shale in the Appalachian Basin. (EIA lower 48 States Shale gas map) The shale gas has become one of the fastest growing portions of the unconventional gas development. (U.S. EIA shale gas review 2011)

â…¡ Hydraulic fracturing

A crucial element that drives the fast- growing development of unconventional gas, especially shale gas, production has been the hydraulic fracturing and horizontal drilling technique. (Marcellus shale Jan 2012) Unlike conventional natural gas formations, the unconventional gas reservoirs, such as coalbed, shale and tight sand, have very low permeability and porosity, which hindered the commercial exploration of these abundant natural gas resources. (Helms horizontal drilling) With the advent of horizontal hydraulic fracturing technique, the oil and natural gas production in the previous inaccessible shale gas reservoirs have become a reality. However, there are growing environmental concerns over this process, such as water availability, wastewater management, water contamination, air pollution, land usage, and so on. Therefore, it is of vital importance to have a comprehensive understanding of how this technology is employed by the industry and its potential impact on the human health and the environment. Besides, we are also concerned about what we can do to prevent or minimize those side effects to achieve a sustainable and environment-friendly development of the natural gas industry.

Hydraulic fracturing technique typically uses a large amount of fracturing fluid, a mixture of water, proppant and chemical additives, which is injected into the drilling wells at extremely high pressure, to crack the target formation and to carry the propping agent down into the newly created fractures. As a result, the porosity and permeability of the gas formation are enhanced, enabling the released gas to flow through the cracked fissures into the wellbore for production. The major component of fracturing fluids is water, followed by the propping agents which are used to keep the newly created fractures open. The chemical additives only account for a small portion (less than 1%) of the overall fracturing fluids, but they are essential for maintaining the proper function of the fracturing fluids. Some of the most commonly used chemical additives include biocide, corrosion inhibitor, gelling agent, breaker, and so on (EPA 2012).

A large number of wells drilled and completed today are operated by the hydraulic fracturing technique. The current fracturing technique includes both vertical and horizontal hydraulic fracturing. In Ohio, most current drilling wells are vertical wells because most currently drilled wells in Ohio are located in conventional oil and natural gas reservoirs, such as sandstone (ODNR 2011). There are some advantages of vertical drilling over horizontal hydraulic fracturing. First, the vertical well is cheaper. The cost of a horizontal well is normally 80% more than the cost of a horizontal well, in some cases can be two to three times (1999 DOE Office of fossil energy, API hydraulic fracturing operations). Furthermore, the water withdrawal of a vertical well is much lower than that of a horizontal well. In the Marcellus shale gas play, a typical vertical well drilled in the unconventional gas formation often needs 500,000 to 1,000,000 gallons of water (a vertical well in the conventional gas formation may only need 5,000 to 50,000 gallons of water), while a horizontal well requires an average of several million gallons of water to complete the whole operation (Harper 2008 PA Geology, OEPA). A vertical well also has much less land usage and community disturbance than a horizontal well.

However, with the discovery and development of the abundant unconventional oil and natural gas resources, the oil and natural gas producers have started relying more and more on the horizontal hydraulic fracturing process. A horizontal hydraulic fracturing well starts with a vertical drilling, which is drilled vertically several thousand feet until it reaches kickoff point. From there, the angle building process begins. The drilling bit takes a curve to the target formation, where the wellbore comes horizontal. Then, the drilling will continue laterally until the desired distance is reached. During the drilling and completion of a horizontal well, a series of protective steel casing and cement layers are installed in the drilling well to isolate the well from surrounding formations. While in the upper part of the well, multiple layers of cement and steel casing are installed to separate the fracturing well and nearby groundwater aquifer, preventing potential groundwater contamination. Unlike vertical drilling process, horizontal drilling operation allows for two or more wells to be drilled from the same well pad, greatly reducing the number of well pads and minimizing land usage and surface disturbance. (Horizontal drilling EIA 1993, West Virginia fracking report 2010) Besides, horizontal drilling can provide much more wellbore exposure to the gas reservoirs than vertical drilling does. In the Marcellus shale gas reservoir, for instance, a vertical well may only be able to be exposed to a natural gas formation for as little as a few tens of feet, while a horizontal operation can get access to 3000 to 4000 feet exposure of such formation, which can bring much higher gas production rate. (Harper 2008 PA Geology,)

Chemical additives

Due to the rapid development of the hydraulic fracturing process, environmental issues related to this technique have attracted more and more attention from all across the country. This process needs large amount of fracturing fluids, a mixture of water, sand and chemical additives, which are injected into the drilling well at extremely high pressure. The fracturing fluids are used to create fractures in the gas-bearing formation and to carry sand or other proppant into the cracked fractures to keep them open after the pressure is released (EPA hydraulic fracturing 2004). The composition of fracturing fluid may vary according to different geological properties of the formation being fractured (Modern shale gas). Different companies may also have different chemical additives in their own fracturing fluids to perform the hydraulic fracturing. For example, some drilling companies use Acrylate phosphonate copolymer as the major components in their scale inhibitor, while some drillers prefer ethylene glycol. (Fracfocus) Figure 1 shows an average mass composition of fracturing fluids. The major components of fracturing fluid are water and proppant, comprising more than 99% of the fracturing fluid. The chemical additives only make up 0.934% (Own results). Table 1 summarizes the major compounds used in each chemical additive and the daily usage of those compounds (EPA hydraulic fracturing study plan, 2011). Even though some of the components in the fluids, such as water, proppant and non-hazardous salts, are harmless, a number of chemicals, such as methanol, Isopropanol, petroleum distillates, used in the fracturing fluid can cause harm. If not disposed of properly, those chemical additives will pose a threat to the environment and public health (Kaufman et al 2008). However, chemical composition of the hydraulic fracturing fluid may vary, depending on the geochemical properties of the formation be fractured, design of the wells or fracturing operation and preference of different companies. Moreover, the chemical additives are not mixed up all together at a time, they are injected into the well separately. For example, diluted acid may be injected into the pipeline first to clean the wellbore, providing a clean pathway for the fracturing fluids, while breaker may be introduced into the fracturing fluids as an independent component when fracturing process is completed. The purpose of adding breaker is to break up the gelling agents, facilitating the recovery rate of the fracturing fluids (EPA hydraulic fracturing 2004).

At present, there are no existing federal laws or regulations requiring full disclosure of chemical additives used in the fracturing fluids (Hatzenbuhler and Centner 2012, Murrill et al 2012, Negro 2012, Hannah 2011), oil and natural gas manufacturers still refuse to provide the proprietary information of their products because of "trade secret". Therefore, it is impossible for the public to have a comprehensive knowledge of what chemicals are injected into the underground during the fracturing process. This what we should do to respond to the potential risks posed to the environment and public health by those unknown chemicals.

Figure 1 Typical percent mass composition of chemical additives used in fracturing fluids

Water

Water is an essential component used in the process of hydraulic fracturing. During the drilling process, water is used for various purposes, including cleaning the wellbore or pipelines, fracturing the gas-bearing formation and transporting the propping agents to the fractures and fissures created (Soeder et al 2009). In general, between 2 million to 6 million gallons of water are needed to complete a fracturing well on Marcellus Shale or Utica Shale (Ohio EPA). However, the amount of water required per well may vary due to the actual geological properties of different wells (Arthur et al ALL Consulting, Nicot et al 2012). Typically, the possible water resources for hydraulic fracturing include surface water, groundwater, municipal water supplies, treated wastewater from wastewater treatment plant and recycled produced water or flowback water (API 2010, Gregory 2011, Nicot et al 2009). In actual process, the selection of water resources will depend on multiple factors, such as water supply volume, quality requirements, cost, geological properties of formation being fractured and local regulatory requirements (API 2010, Cooley et al 2012). In Ohio, the main source of water for hydraulic fracturing is surface water (Ohio hydrfracking review).

Proppant

Proppant is a major component in the hydraulic fracturing fluids, comprising about 9% of the total mass composition. The purpose of proppants is to keep the created fractures and fissures open after the introduced pressure is released so that the natural gas can escape from freely from the target formation (McDaniel et al 2012). Commonly used propping agents contain sand and ceramic materials (Authur et al 2009). Several aspects considered when drilling operators select proppants are: cost-effect (proppant should be more economical), conductivity (proppant should provide sufficient conductivity in the target formation to achieve the optimal gas production) and durability (proppant should be able to function in the created fractures and fissures for a longer period of time) (Shah et al 2010).

Acids:

Acids are the basic component of hydraulic fractring fluid. The most commonly utilized acid is 15% hydrochloric acid. Acids are used to clean up perforations and pipelines, providing a clean pathway for the fracturing fluids to flow through. Acids can also open fractures near the wellbore to help initiate cracks in the target formation. Concentrated acids are corrosive and highly hazardous. However, acids used in the hydraulic fracturing process are usually diluted with fracturing fluids before injection into the drilling wells. Therefore, the concentration of acids in the injected fluids is generally much lower than its original form (EPA hydraulic fracturing, 2004).

pH adjusting agents:

pH adjusting agents are added into the hydraulic fracturing fluids to maintain the pH of the fluids to enable other chemical additives to function properly. Most common pH adjusting agents are sodium hydroxide, potassium hydroxide, acetic acid, sodium carbonate and potassium carbonate.

Gelling agents:

One of the major functions of water in the hydraulic fracturing process is to carry the propping agents down into the target formation. However, low viscosity of water limits this ability. Therefore, gelling agents are used to increase the viscosity of hydraulic fracturing fluid (EPA hydraulic fracturing, 2004). In general, there are three types of gelling agents: linear gels, cross-linked gels and foamed gels.

Linear gels

Linear gels are typical gelling agents used to increase the viscosity of hydraulic fracturing fluid. The addition of linear gels can enhance the proppant transport performance of fracturing fluid, improving the drilling efficiency and gas production. The most commonly used linear gels include guar gum, guar gum derivatives and cellulose derivatives, which are harmless to the environment. However, some toxic chemical substitutes may also be used in linear gels. For example, diesel fuel, which is capable of boosting the dissolution of linear gelling agents, has been found in some hydraulic fracturing fluid. (Wiseman 2009) Diesel fuel is a mixture of different organic compounds, which may contain known hazardous and toxic chemicals, such as benzene. (Adam et al 1999)

Cross-linked gels

Compared to traditional linear gels, cross-linked gels can provide even better thickening effects of the hydraulic fracturing fluid and enable the fluid to remain viscous for a longer time. The most commonly used chemicals in cross-linked gels involve boric acid, sodium tetraborate decahydrate, ethylene glycol, and monoethylamine. Direct contact with those chemicals can cause eye, skin and respiratory damages. (EPA 2004)

Foamed gels

Foamed gels are also frequently used to thicken the hydraulic fracturing fluid. (Penny et al 1993) The foaming technology uses a mixture of gas and foaming agents to enhance the viscosity of hydraulic fracturing fluid. Nitrogen and carbon dioxide are the most common gases utilized in the foaming agents. (Gaydos et al 1980) Foaming agents may contain diethanolamine, isopropanol, ethanol, and 2-butoxyethanol. Direct contact with these chemicals can harm eyes, skin and respiratory tract and cause chronic effects, such as cancer. (EPA 2004)

Biocide:

Due to the large amount of water required for the completion of hydraulic fracturing process, the water used in the fracturing process is usually stored on site in tanks or pits, which are open to the atmosphere. Bacteria in the air, rain or dust can easily get into the water. In addition, the organic chemical additives can provide nutrient sources for microbes in the hydraulic fracturing fluid. (Struchtemeyer 2012) As the microbes grow, they may secrete unwanted byproducts that degrade chemical additives or corrode equipment. (Dawson et al 2012) To avoid the occurrence of bacterial contamination, biocide is used to control the microbial growth in the hydraulic fracturing fluid. Commonly used biocides in the hydraulic fracturing fluid include Hydroxymethyl, phosphonium sulfate (THPS), sodium hypochlorite, didecyldimethylammonium chloride (DDAC), tri-n-butyl tetradecyl phosphonium chloride (TTPC) and glutaraldehyde. (Struchtemeyer 2012)

Breaker:

After the target formations have been cracked by the fracturing fluids and proppant mixtures that are injected into the drilling well, the pressure in the well is usually released for a period of time, during which the fracturing fluids flow back up to the surface to be stored in tanks or pits for further treatment. (Harris 1988) The high viscosity of the fracturing fluids prevents good recovery of fracturing fluids during this period. Therefore, breakers are added into the viscous fluids to decrease the viscosity of the fracturing fluids, enhancing the clean-up of the fracturing fluids from the wells. (Rae et al 1996) The common chemicals contained in the breaker include ammonium persulfate, ammonium sulphate, copper compound, ethylene glycol and glycol ethers. (FracFocus website)

Corrosion inhibitor:

Due to the acids used in the fracturing process to clean perforations, dissolve minerals and initiate cracks in the target formation, there is high possibility of corrosion occurring in the wells. (Sitz et al 2012) Hence, it is of great importance to add corrosion inhibitor to prevent the possible corrosion. Corrosion inhibitors can remove corrosive agents, such as oxygen, from the fluids or adsorb on the surface of metals to inhibit the corrosion reaction. (Rostami et al 2009) The corrosion inhibitors may contain Propargyl alcohol, Pyridium, Ethylmethyl derivatives, Chlorides, Poly-(oxy-1,2-ethanediyl)-nonylphenyl-hydroxy. Direct contact with these chemicals can cause damage to eyes, skin and nervous system. (EPA 2004)

Friction reducer:

To achieve the optimal production rates of natural gas, fracturing fluids are supposed to be injected into the drilling wells at very high speed under extremely intense pressure. (Kaufman et al 2008) The high speed and high pressure will definitely cause increasing friction between the fluids and pipelines. In order to minimize the friction during fracturing processes, friction reducers are added into the fracturing fluids. The most commonly used friction reducers may include latex polymers or copolymers of acrylamides. (EPA hydraulic fracturing)

Iron control:

The use of acids in the fracturing process may cause level of dissolved iron in the fracturing fluids. (Walker et al 1990) The sources of iron can be from iron-containing minerals in the formation, from dissolved rust or debris in the pipeline, or from the tanks or pits that used to store the acids and waster. (Taylor et al 1999) The iron can precipitate when contacted with oxidants at proper situation. Iron precipitation during the fracturing process can reduce the efficiency of gas production. (Taylor et al 1999) Therefore, the iron control agents are necessary to inhibit the iron precipitation. The most common iron control additives include citric acid, citric acid salts, sodium citrate and ammonium citrate and polyamino carboxylates. (FracFocus website)

Scale inhibitor:

The water used for hydraulic fracturing is generally from fresh water sources, such as lake, river and streams, groundwater, and recycled water from flowback water. (Ohio EPA, 2012) These water sources may contain a certain amount of dissolved minerals. (Cheremisov et al 2008) In addition, the acid treatment of formation can also dissolve high concentration of minerals. (Shen et al 2011) Inorganic scale precipitation, such as Calcium sulfate, calcium carbonate and barium sulfate, is very common problems during the hydraulic fracturing processes. (Cheremisov et al 2008) The scale problems can cause contrary effects on the production of drilling wells. For example, the scale deposition can decrease the reservoir permeability, reduce flow rates of fracturing fluids and block the pipelines or perforations, which can cause lower gas production rates. (Cheremisov et al 2008) Scale inhibitor is utilized to prevent the scale precipitation in the fracturing fluids. The common scale inhibitors contain copolymer of acrylamide and sodium acrylate, sodium polycarboxylate and phosphonic acid salt. (FracFocus website)

Surfactant

The major application of surfactant in fracturing fluids is to reduce the surface tension, enhancing the recovery of fracturing fluids injected into the drilling wells. (Kaufman et al 2008) Unlike conventional gas formation, unconventional gas formation, such as coalbed methane, tight sands and shale, have low permeability. (USGS 2006) In unconventional gas-bearing formations, fracturing fluids can be trapped in the small pores and fractures after the formations are cracked, which is caused by the capillary forces. Reducing the capillary forces can significantly improve the recovery of fracturing fluids. (Harris 1988) Therefore, the surfactant is introduced into the fracturing fluids. The common surfactants include lauryl sulfate, ethanol, naphthalene, methanol, isopropyl alcohol and 2-butoxyethanol. (FracFocus website)

Clay stabilizer

Another chemical additive that may be added into the fracturing fluids is clay stabilizer, which is used to prevent the clays from swelling and shifting. (FracFocus website) During the hydraulic fracturing operation, large amount of water and additives are injected into deep underground. Ion exchange reactions between clay and the introduced fluids can induce dissolution of clay, resulting in reduced clay stability, such as clay swelling. (Wangler et al 2008) When clay swelling occurs, permeability of the gas-bearing formation is decreased, which can greatly impede the gas production rate. (Zhou et al 1998) Thus, clay stabilizer is utilized in the hydraulic fracturing fluids to minimize the damage caused by clay swelling. Commonly used clay stabilizers include choline chloride, ammonium chloride, sodium and potassium chloride.

Table 1

Additive type

Main Compound(s)

Purpose

Water

H2O

Carrier or base fluid

Proppant

Silica, quartz sand

Keep fractures and fissures open.

Diluted Acid

Hydrochloric acid or muriatic acid

Help dissolve minerals and initiate cracks in the rock

Biocide

polycyclic organic matter and polynuclear aromatic hydrocarbons

Eliminate bacteria in the water

Breaker

ammonium persulfate, ammonium sulphate, copper compound, ethylene glycol and glycol ethers

Allow a delayed break down of the gelling agents

Corrosion inhibitor

Propargyl alcohol, Pyridium, Ethylmethyl derivatives, Chlorides, Poly-(oxy-1,2-ethanediyl)-nonylphenyl-hydroxy.

Prevent the corrosion of the pipe

Crosslinker

boric acid, sodium tetraborate decahydrate, ethylene glycol, and monoethylamine

Maintain fluid viscosity as temperature inreases

Friction reducer

latex polymers or copolymers of acrylamides

Minimize friction between the fluid and pipe

Gelling agents

Guar gum, hydroxyethyl cellulose, diesel fuel, diethanolamine, isopropanol, ethanol, and 2-butoxyethanol

Thicken the fluids in order to suspend the sand

Iron control

citric acid, citric acid salts, sodium citrate and ammonium citrate and polyamino carboxylates

Prevent precipitation of metal oxides

pH adjusting agent

sodium hydroxide, potassium hydroxide, acetic acid, sodium carbonate and potassium carbonate

Adjust pH and maintain he effectiveness of other components

Scale inhibitor

copolymer of acrylamide and sodium acrylate, sodium polycarboxylate and phosphonic acid salt

Prevent the scale deposits in the pipe

Surfactant

lauryl sulfate, ethanol, naphthalene, methanol, isopropyl alcohol and 2-butoxyethanol

Used to reduce the surface tension and capillary forces

Clay stabilizer

choline chloride, ammonium chloride, sodium and potassium chloride.

Prevent clays from swelling or shifting

â…¢ Environmental and social effects

As the hydraulic fracturing technique advances, the associated environmental concerns have arisen, which has attracted the attention of the whole country. These problems include……….

Water availability

In a hydraulic fracturing process, between 2 to 6 million gallons of water is needed to complete the operation. (Ohio EPA) The major source of water is local rivers, lakes, groundwater or other fresh water reservoirs. This large amount of water may place a burden on the local water supply, especially in areas with limited fresh water resources. Withdrawal of water in drought or low stream flow period can also have a great impact on aquatic life, recreational activities, municipal and industrial water supplies. Many states in the United States have issued laws to regulate the water withdrawal from local fresh water reservoirs. In Ohio, withdrawal of water over 2 million gallons per day for more than 30 days must get a permit from the Ohio Department of Natural Resources. (Ohio EPA) Therefore, it is of vital importance for the drilling companies to guarantee the water needs to complete the hydraulic fracturing process without conflicting with other local water demands before they start the drilling. (Entrekin et al 2011)

Disposal of wastewater

It is reported that 10-70% of the fracturing fluid injected into the drilling well returns to the surface for further treatment and handling (EPA 2012). The disposal of the wastewater produced in the drilling and completion of the hydraulic fracturing process is one of the most frustrating problems at present. There are two types of wastewater, flowback water and produced water. Flowback water is "the water that returns to the surface from the wellbore within the first few weeks after hydraulic fracturing. It is composed of fracturing fluids, sand, and water from the formation, which may contain hydrocarbons, salts, minerals, naturally occurring radioactive materials", while the produced water refers to "the water that is brought to the surface during the production of oil and natural gas. It typically consists of water already existing in the formation, but may be mixed with fracturing fluid if hydraulic fracturing was used to stimulate the well." (DOE Hydraulic fracturing operation 2012)

The main concern with flowback and produced water is the extremely high concentration of total dissolved solid (TDS). TDS is a measurement of dissolved inorganic and organic substances in water. Under the National Secondary Drinking Water Regulations, the U.S. Environmental Protection Agency classifies TDS a secondary drinking water contaminant, and the non-enforceable maximum contamination level for TDS is 500mg/L. While, the TDS concentration of flowback and produced water is usually much higher than that standard, ranging from more than 1000mg/L to 400,000mg/L or even higher. (USGS produced water 2011, Chapman 2012, Hayes 2009) Inorganic components, such as chloride, sodium, magnesium, calcium, contribute most to the concentration of TDS of the hydraulic fracturing wastewater. (Chapman 2012, Penn State extension wastewater) Besides, the wastewater may also contain heavy metals, trace elements or other unknown chemical contaminants. If not disposed properly, the wastewater can pose a major threat to the environment. Currently, the disposal methods include:

Deep injection

The primary and most common disposal method for the flowback and produced water is deep underground injection. (Modern shale gas) In this method, wastewater from the fracturing process is injected into the deep disposal wells, far below the underground drinking water aquifer. Now, there are 6 classes, I, II, III, IV, V, VI, of injection wells in the United States, the class II wells are used for the oil and natural gas related waste. More than 2 billion gallons of flowback and produced water is discharged into the approximate 144,000 class II wells in the U.S. (US EPA) Injection wells are regulated under the Safe Drinking Water Act, all the Class II wells must meet the minimum requirement in the Underground Injection Control (UIC) programs or the state level standards. (US EPA)

Wastewater treatment plant

Municipal or industrial wastewater treatment plant is another treatment option for the flowback and produced water. Oil and natural gas companies can transport the wastewater from the fracturing process to the nearby municipal or industrial wastewater treatment plants for further processing. The treated water, which should conform to the standards regulated by the laws, can be recycled or discharged into surface water bodies. However, suitable wastewater treatment plants may be limited in some areas because of the existing sufficient domestic and industrial wastewater load or technological capacity. Most municipal wastewater treatment plants use biological technique to treat the wastewater, which may not be effective to treat the flowback and produced water with high concentration of TDS.

Reuse

An additional choice for oil and natural gas companies to deal with the briny flowback and produced water is recycling. Recycling has become more and more popular because the cost of reuse is cheaper than other disposal options. Typically, it is easier and more economical to treat the brine water to a level suitable for the use for further hydraulic fracturing process. (Modern) Besides, recycling can also reduce the potential fresh water demand and subsequent disposal and handling. Some oil and natural gas companies have been focusing on total recycling. (Stephen 2011 from flowback to fracturing)

Water contamination

Water contamination is also a growing concern associated with hydraulic fracturing process. Millions of gallons of fracturing fluids, consisting of water, sand and chemical additives are injected into the deep underground formation to release natural gas. The chemical additives only make up a small component of the fracturing fluids. However, given the large amount of fracturing fluids required to complete the drilling operation, the total mass of chemicals used in hydraulic fracturing process is still considerable. Minority Staff of United States House of Representatives Committee on Energy and Commerce conducted a study investigating the chemical usage of fracturing fluids of 14 oil and natural gas service companies between 2005 and 2009. In this study, they concluded that these companies consumed "780 million gallons of hydraulic fracturing products" during this period of time. The common used chemicals in the 14 oil and natural gas service companies’ products contain 29 toxic chemicals, including 13 carcinogens. In addition, 24 different hazardous air pollutants were contained in their fracturing fluids. The most commonly used chemicals in the hydraulic fracturing products are methanol, isopropanol, crystalline silica, ethylene glycol monobutyl ether and ethylene glycol. (Minority Staff of H. Comm. on Energy and Commerce, 112th Cong., Chemicals Used in Hydraulic Fracturing 5, 9(2011)) Leakage, spills or improper disposal of these chemical additives may extremely threaten the fresh water aquifer.(Kargbo et al 2010)

What make the situation even worse is that many of the chemicals used in the fracturing fluids are unknown. (West Virginia) At present, there are no existing federal laws or regulations requiring disclosure of chemical additives used in the fracturing fluids (Murrill et al 2012), oil and natural gas manufacturers refuse to provide proprietary information of their products because of "trade secret". Therefore, it is impossible for the public to have a comprehensive understanding of what chemicals are injected into the underground during the fracturing process and what we should do to respond to the potential risks posed to the environment and public health by those unknown chemicals.

Land usage

With the development of oil and natural gas came the associated land usage issues. To complete a well construction, the drilling company shall install well pad, construct tanks or pits to store water, chemical additives and wastewater, and build up roads for the transportation. The amount of land required in the drilling area may vary due to different drilling conditions. Based on the data provided by the Bureau of Land Management, a shallow vertical well drilled in Arkansas may take 2.0 acres for well pad, 0.1 miles for road construction, and 0.55 miles for utility facilities, making a total area of around 4.8 acres. However, a horizontal well typically uses a larger well pad approximately 3.5 acres and the total area of surface disturbance rises to 6.9 acres. (Bureau of land management) Given the 514,637 producing gas wells (as of the end of 2011, EIA) in the United States, the overall land usage related to the hydraulic fracturing industry is surprising considerable.

Community disturbance

In addition to the land use impact, hydraulic fracturing process can greatly affect community’s life. During the first a few months of the hydraulic fracturing process, workers clear the drilling area, transport water, chemical additives and pipelines, install the well pad, set up the drilling rig, construct storage tanks or pits, drill the well, install the pipelines, fracture the formation and prepare for the production of the well. If multiple wells are drilled at the same area, the process can be extended for a longer time.

In this period, the process may produce waste, noise, dust, light pollution and other unwanted byproducts to the nearby community. Besides, the truck traffic is another major impact. The hydraulic fracturing operation needs a large amount of fresh water, sand, chemical additives, pipelines and operation facilities. Moreover, substantial flowback and produced water should be disposed of during and after the fracturing process. Therefore, trucks are used to carry those staff to or off the drilling area, dramatically increase the traffic burden of local area.

Air pollution

Hydraulic fracturing process can also produce numerous air pollutions, such as volatile organic compounds (VOCs), methane, benzene and other toxic air pollutants. (EPA) According to U.S Environmental Protection Agency, oil and natural gas industry is the dominant source of industrial emission of VOCs. In 2008, the VOC emission from oil and natural gas industry is approximately 2.2 million tons. (http://www.epa.gov/airquality/oilandgas/basic.html) The oil and natural gas industry also is a primary producer of methane, which is the major component of natural gas. Methane can be emitted into the atmosphere during drilling, fracturing or gas producing process. As the extensive growth of oil and natural gas industry, the air issues associated with it have been an increasing concern. States, such as Wyoming, Colorado, Utah and Texas experienced and documented air quality impact from the hydraulic fracturing process. The U.S. EPA has been focusing on issuing relevant laws to limit the harmful air pollutant produced from this industry.

â…£ Regulation

Federal regulations

Safe Drinking Water Act

"The Safe Drinking Water Act (SDWA) was established to protect the quality of drinking water in the U.S. This law focuses on all waters actually or potentially designed for drinking use, whether from above ground or underground sources." (http://www.epa.gov/lawsregs/laws/sdwa.html ) The SDWA authorizes EPA to set up minimum standards to protect the safety of drinking water. In 2005, congress amended the SDWA, excluding hydraulic fracturing from Underground Injection Control regulation under SDWA § 1421 (d) via the Energy Policy Act. (http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturing/wells_hydroreg.cfm )

Clean Water Act

"The Clean Water Act (CWA) establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. The basis of the CWA was enacted in 1948 and was called the Federal Water Pollution Control Act, but the Act was significantly reorganized and expanded in 1972. "(http://www.epa.gov/lawsregs/laws/cwa.html) The hydraulic fracturing process uses massive amount of fracturing fluids, around 30%-70% of the fracturing fluids return back to the surface, containing high concentration of total dissolved solid and other harmful components. The Clean Water Act regulates the oil and natural gas company to properly dispose of the wastewater produced during the fracturing process, protecting surface water and groundwater from potential contamination.

Clean Air Act

"The Clean Air Act (CAA) is the comprehensive federal law that regulates air emissions from stationary and mobile sources. Among other things, this law authorizes EPA to establish National Ambient Air Quality Standards (NAAQS) to protect public health and public welfare and to regulate emissions of hazardous air pollutants."(http://www.epa.gov/lawsregs/laws/caa.html) Because of the numerous air pollutants produced by the hydraulic fracturing process, the Clean Air Act regulates the oil and natural gas company to control the emission of toxic air pollutants from their drilling process. For example, the National Emissions Standards for Hazardous Air Pollutions has established standards for the emission of major air pollutants from the oil and natural gas production facilities.

Ohio Regulations

Ohio is one of the leading producers of oil and natural gas in the United States. Almost half of Ohio sits over two of the major shale gas plays, Marcellus shale and Utica shale. It is expected that the state will experience a remarkable boost in the oil and natural gas drilling activities in the near future. The Ohio Environmental Protection Agency and Ohio Department of Natural Resource have established several laws and regulations to regulate the development of the oil and natural gas industry, protecting the public and environment. (Ohio’s regulation OEPA) These laws and regulations include House Bill 278, Senate Bill 165, Senate Bill 315 and so on. (ODNR http://www.dnr.state.oh.us/oil/oilgashome/tabid/10371/Default.aspx)

The House Bill 278 was passed on August 11, 2005. This bill is "a listing of terms and conditions that the agency could attach to drilling permits issued for wells and associated facilities that are to be located within urban areas". (Ohio Law summary ODNR) The Senate 165 became effective on June 30, 2010. "It represents the first major change to ORC 1509 in 25 years and reaffirms that the DMRM has the sole and exclusive authority to regulate the permitting, location, spacing and production operations of oil and natural gas wells. Ohio’s oil and natural gas law and the rules adopted under it constitute a comprehensive plan with respect to all aspects of the siting, drilling and operations of oil and natural gas wells." (Ohio Law summary ODNR)

The Senate Bill 315 was signed by the Ohio Governor on June 11, 2012. This Ohio’s new law has become one of the strictest laws in the nation for regulating the development of oil and natural gas industry. (http://www.ohiodnr.com/tabid/23947/Default.aspx) Some key points of the Senate Bill 315 include: 1) Discloses chemicals used in all the processes of hydraulic fracturing, including the proprietary chemicals; 2) "Requires the well operator to take water samples within 1,500 feet of a proposed horizontal well and disclose the results in their permit application." 3) Requires well operators to disclose the source of water used in the hydraulic fracturing processes.

â…¤ Summary and Outlook

Natural gas is a naturally occurring hydrocarbon gas mixture, primarily containing methane, which has been a widely used energy source in many applications since it is cleaner, safer and cheaper. With the development of hydraulic fracturing technique, the extraction of natural gas from unconventional energy gas plays, such as coal bed, tight sands and shale reservoirs, has been playing a more important role in the supply of natural gas across the country. However, even though the development of energy sources is essential to the economy, the impacts of hydraulic fracturing on the environment and water sources should not be ignored. The fracturing fluid contains about 90% water, 8% sand proppant, and less than 2% other chemical additives, some of which may be toxic to the public if released in the environment. Besides, some chemicals in the fracturing fluids are listed as trade secrets by the drillers, making it difficult for the analysis of water contamination caused by the fracturing fluids. Contaminants in flowback fluids also come from naturally occurring substances, such as salts, metals and radioactive chemicals that are found deep underground since 30%-70% of the fluids will come back to the surface along with the underground toxic substances as we as the gas. Therefore, the federal and state government should establish stricter laws to regulate this fast-growing industry and enable the public to better understand the hydraulic fracturing process. Besides, oil and natural gas companies should be required to disclose all the chemicals they use during the hydraulic fracturing operation, which is essential for the study of toxicity, transport and disposal of the fracturing fluids and the associated wastewater.