The US experience shows that there are many accidents that cause damage to the environment and human health. Documented violations of legal requirements range from 1-2% of all facilities that have received drilling permits. A large number of such accidents occur due to improper handling of equipment and leaking equipment. Moreover, groundwater contamination with methane is recorded in the vicinity of gas wells, which in extreme cases leads to explosions of residential buildings, as well as potassium chloride contamination, which leads to salinization of drinking water. The degree of impact increases as shale gas deposits are developed at high density, with up to 6 wells per square kilometer.

Greenhouse gas emissions

The process of fugitive methane leakage from hydraulic fracturing can have a huge impact on the greenhouse gas balance. Existing estimates range from 18 to 23 g CO2 equivalent per megajoule from the exploration and production of unconventional natural gases. Methane emissions into aquifers have not yet been estimated. However, emissions at individual facilities can vary tenfold depending on well productivity.

Depending on some factors, greenhouse gas emissions from shale gas relative to its energy reserves are as low as those from natural gas transported over long distances or as high as those from coal, which goes through a full life cycle from extraction to combustion.

The EU regulatory framework

The task of mining law is to create a common regulatory framework for mining activities. The aim is to promote the prosperity of the manufacturing sector, secure energy supplies and ensure adequate protection of health, safety and the environment. At the EU level, there is no comprehensive regulatory framework for extractive industries.

However, there are 4 specially developed directives that regulate the extractive industry. In addition, there are many rules and directives that do not specialize in the regulation of extractive relations, but affect the extractive industry. Focusing on regulations related to the environment and human health, the 36 most relevant directives from the following areas of law were identified: water law, environmental protection, safe working conditions, radiation protection, waste law, chemical law and accident law.

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Shale gas production – how is shale gas extracted?

As with many other methods of mineral extraction, shale gas production technology consists of several crucial stages:

• Exploration;
• Drilling a network of wells;
• Installation of gas collection equipment;
• Creation of hydraulic fractures;
• Gathering and sorting of the products obtained from the wells.

Exploration.
At this stage, the company planning to produce gas evaluates profitability and other indicators related to production and environmental impact. If the environmental standards are in line with the legislation of the region, the process of drilling several test wells begins. Samples will be taken from them to determine the amount of gas contained in the shale. If everything is in order, the company proceeds to the next stage of work.

Drilling
The process of drilling wells in shale gas production is quite different from the standard “just drill a deep hole in the ground”. The thing is that, unlike the traditional method of gas extraction from gas deposits, this scheme does not work with shale gas. The main difference is the fact that shale gas is not in a conventional “gas bubble underground”. It is contained in the tiny pores of the shale formation located horizontally below the surface. Thus, having drilled a vertical well to a certain depth, it is diverted to a horizontal plane and drilled further as long as necessary. Thus, several (possibly dozens) of such wells are created at the production site.

After the direct drilling process, the wells are sealed. This is necessary to prevent the uncontrolled release of gas and other chemicals associated with production. In simple terms, the inserted pipes are insulated with various hermetic seals that do not allow gas to flow to the surface.

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The pressure causes tiny cracks to form that allow the gas to escape. This entire fracture system connects the well to the productive parts of the reservoir away from the bottomhole. To prevent the fractures from clamping together after the pressure is reduced, coarse sand is added to the fluid injected into the well. The radius of fractures can reach several tens of meters.

The fracture process is highly dependent on the physical properties of the fluid and, in particular, its viscosity. In order for the fracture pressure to be lowest, it is necessary for it to be filterable. Increasing the viscosity as well as reducing the filterability of fluids used in fracturing is accomplished by introducing appropriate additives. Such thickeners for hydrocarbon fluids used in fracturing are salts of organic acids, wax molecular and colloidal compounds of oil (e.g., oil tar and other oil refining wastes).

Some oils, kerosene-acid and oil-acid emulsions used in fracturing carbonate reservoirs, and water-oil emulsions have significant viscosity and high sand-bearing capacity. These fluids are used as fracturing fluids and sand-bearing fluids when fracturing oil wells.

The use of hydrocarbon-based fracturing fluids and sanding fluids to fracture formations in water-injection wells can lead to deterioration of water permeability due to the formation of water-hydrocarbon mixtures. To avoid this phenomenon, formations in water injection wells are fractured with thickened water. Sulfide-alcoholic bordeaux (SAB) and other cellulose derivatives that are well soluble in water are used for thickening. As a rule, fluids used in hydraulic fracturing are carcinogenic. A special danger is the possibility of chemical reagents used in hydraulic fracturing getting into formations containing artesian water used for drinking.

The main environmental hazard in shale gas extraction is the use of large quantities of chemicals that are mixed with water and sand. Hydraulic fracturing (fracking) has to be repeated up to 10 times a year in one area. During fracking, the chemical mixture soaks into the rock, contaminating large areas as well as groundwater.

This is why shale gas extraction has been banned in New York State in the USA. In Europe, where environmental legislation is stricter than in the USA, this may be the main reason why shale gas extraction will not become more widespread.

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