A recent article in the journal "Energy Policy" identifies five critical points of shale gas production and suggests mitigation strategies. 

Reducing pollution at five critical points of shale gas production: Strategies and institutional responses (Weblink)

From experiences in the United States, careful consideration of five critical points relating to shale gas production can form the basis for developing strategies to minimize environmental and health risks: (1) casing and cementing, (2) handling wastewater, (3) venting and flaring, (4) equipment with air emissions, and (5) seismic events. 

For each strategy, institutional responses to markedly reduce the risks of harm to people and the environment are identified. These responses offer state and local governments ideas for enabling shale gas resources to be developed without sacrificing public health and environmental quality.

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The full text of the publication is accessible to subscribers of the journal, non-suscribers have to pay a fee. SHIP provides an example of the ideas of the author with an excerpt of the text, relating to points (1) casing and cementing and (2) handling wastewater:

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2. Enumerating five critical points

A wide range of issues and problems have been associated with the development of America's shale gas resources. Highlighting five critical points identifies prominent sources of pollutants that can be reduced by adopting strategies implemented through institutional responses.

2.1. Casing and cementing

A major concern has been deleterious material leaking from shale gas wells, and many of these problems are associated with faulty casing and cementing. A study from Pennsylvania found that 3.3% of violations involved casing and cementing (Considine et al., 2013). Many persons with water wells in proximity to shale gas wells have complained about contaminated water from fracturing fluids (Brantley et al., 2014). Research from the United States shows methane contamination of aquifers (Osborn et al., 2011 and Vengosh et al., 2013). One study showed the concentration of methane in drinking water was related to the distance to a shale gas well and that distance was the dominant statistical factor in these concentrations (Jackson et al., 2013).

Since shale gas in the United States is generally located 1500–2500 m underground, layers of rock strata prevent leakage of contaminants into an aquifer. This suggests that contamination of groundwater should not be a problem unless the wellbore is faulty. Fugitive gas contamination problems are related to poor casing and cementing (Darrah et al., 2014). Research indicates gas migration as occurring after the conclusion of cementing jobs during the transition from slurry to solid cement (Soeder et al., 2014). In addition, faulty casings or cementing of wells can allow gases to migrate to drinking water supplies (Davies et al., 2014). This leads to a conclusion that greater oversight of wellbore integrity involving casing and cementing requirements can reduce contamination problems (Osborn et al., 2011 and Jackson, 2014).

2.2. Handling wastewater

The public is rightfully concerned about water pollution from fracturing fluids, flowback, and produced water. Some feel that U.S. state enforcement efforts are not very robust, violators are rarely penalized, and penalties are so weak that drilling firms find it cheaper to pay occasional penalties rather than comply with the law (Sumi, 2012). Because fluids used to fracture wells generally contain toxic substances, and the fluids exiting a well may contain additional toxic materials from the rock strata, these liquids must be handled carefully (Vengosh et al., 2014, Vidic et al., 2013 and Werner et al., 2015). Vehicular accidents and faulty storage structures may result in the release of toxic materials (Vinciguerra et al., 2015). Given the potent concentrations of selected toxic chemicals, a small spill or leak can have pronounced affects.

Although difficult to calculate, spills and releases of toxic substances associated with oil and gas wells are thought to be between 0.4 and 12.2 spills per 100 wells drilled (U.S. EPA, 2015a). One study suggests that about 3.4% of wells received notices of violations for well construction problems (Brantley et al., 2014). This suggests that efforts to reduce accidents and contain spills are important.

Related to these contamination events is the secrecy of chemical compounds used in hydraulic fracturing. Under U.S. state law, firms can decline to specifically identify any toxic compound that they feel is a trade secret (Centner, 2013 and Hall, 2013). The U.S. EPA (2015b) estimates that 11% of all ingredient records were designated as confidential business information, and other research found considerable nondisclosure of all compounds used in fracturing wells (Konschnik and Dayalu, 2016). This creates a situation in which persons may not realize their health maladies are related to a pollutant release from shale gas development. Given the pollutant releases, spills, and accidents that have accompanied shale gas development in the United States, drilling firms may need to make greater investments in suitable precautionary measures to avoid accidents and mishaps. Simultaneously, governments can do more to address damages from contamination events.

[…]

3. Discussion and potential responses

The absence of meaningful oversight of shale gas extraction activities by the U.S. federal government meant that state governments had to become more vigilant in protecting their citizens from health and environmental damages. The American experiences show that limitations imposed by democracy, division of powers among levels of governments, and economic challenges imposed by the 2008 financial crisis contributed to inadequate governmental responses. Over the past few years, citizens have petitioned governments to reduce externalities accompanying shale gas development and U.S. state governments have taken steps to provide greater protection for public health.

The identification of five critical points from which too many pollutants are discharged enables local policy-makers to address definitive pollution issues with strategies geared toward achieving reductions of pollutant releases. Moreover, industry can evaluate strategies and become more proactive in developing mechanisms to protect the public and the environment from damages. For each of the five critical points, two or more strategies are identified for responding to unnecessary discharges of pollutants and institutional responses are presented to assist governments in meeting their responsibilities in protecting people and the environment.

[…]

3.1. Reducing damages from casing and cementing

While most governments have already set out fairly comprehensive regulations that are appropriate for ensuring quality casing and cementing (Illinois Hydraulic Fracturing Regulatory Act, 2013), they may be able to do more by enacting, overseeing, and enforcing additional cementing and casing regulations to protect drinking water supplies (Table 1). Specialized provisions can mandate more strict regulation, such as compliance with American Petroleum Institute standards, so that firms cannot legally engage in lesser practices. In placing responsibilities on drilling operators, Texas mandates the use of best currently available technology for some situations and that all potentially productive zones be isolated and sealed off (Texas Administrative Code, 2016).

Two funding ideas are being employed to respond to casing and cementing problems (Dana and Wiseman, 2014). State law can require drilling firms to have mandatory insurance liability coverage. A requirement for restoration bonds can collect funds for subsequent use in restoring damaged environments.

Another idea to address potential water pollution from faulty casing and cementing is to adopt a legislative provision establishing a presumption on liability for new wells being drilled. In Pennsylvania, the legislature adopted a presumption that pollution of water near new oil or gas well within a time frame is presumed to come from drilling the oil or gas well (Pennsylvania Consolidated Statutes, 2016). These ideas show that, through more comprehensive provisions assigning responsibilities and liability, governments can help firms further reduce contamination events and damages related to faulty cementing and casing.

3.2. Reducing damages from wastewater

More exacting regulatory provisions can lead firms engaged in drilling activities to take actions that should reduce contamination events and damages from wastewater (Table 2). One major proposal to facilitate timely responses to exposure to hazards is greater disclosure of the chemical compounds used at a well site. In 2015, the U.S. federal Bureau of Land Management adopted a regulation to limit the non-disclosure of chemical compounds used at wells on federal lands (U.S. CFR, 2015). While the listed details of this regulation do not require disclosure of all compounds, a person will need to sign the affidavit justifying non-disclosure. This may encourage firms to release additional information.

A second idea to reduce damages from wastewater is to allow local governments to enact controls they feel are necessary to protect their citizens. Local governments were formed to enable citizens to address matters of local concern and may be in the best position to quickly respond to a problem (Centner and Kostandini, 2015). U.S. state governments should not be preempting local controls as has occurred in New York and Ohio (New York Environmental Conservation Law, 2015 and Ohio Revised Code Annotated, 2015).

Third, a certification program may be adopted with a provision that precludes discharges of wastewater. The certification program offered by the Center for Sustainable Shale Development (2015) precludes direct or indirect intentional discharges of shale wastewater to surface water except as provided by their standard (Table 2). Another idea is to increase severance tax collections and use the funds to respond to negative externalities (Rabe and Hampton, 2015). Governments can select the recipients of the funds to address those issues most worthy of financial assistance (Colorado Revised Statutes, 2015).

[…]

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