Natural Gas and the Environment

By HSE East Africa | Tuesday Sep 26, 2017

Dodsal Hydrocarbons & Power (Tanzania) Pvt. Ltd. (Dodsal) recently advertised a tender for the provision of technical and consultancy services for carrying out and issuing an Environmental Impact Assessment (EIA) Report for drilling exploration/Appraisal wells along with testing /flaring activities in onshore Ruvu Block. This is in preparation for a drilling campaign scheduled to take place through 2018.

The proposed contract will cover planning, generation and delivery of EIA Report and EIA certificate. The scope will generally include the provision of report and NEMC certificate and detailed delivery schedule, site visits, generation of Terms of Reference, preparation of a scoping report, provision of background information document, regular meetings and reporting to both Dodsal and relevant Environmental authorities.

Exploration for natural gas is likely to have a wide range of negative impacts on the environment. When geologists explore for natural gas deposits on land, they may disturb vegetation and soil with their vehicles. Drilling a natural gas well on land may require clearing and leveling an area around the well site. Well drilling activities produce air pollution and may disturb people, wildlife, and water resources. Laying pipelines that transport natural gas from wells usually requires clearing land to bury the pipe. Natural gas production can also produce large volumes of contaminated water. This water requires proper handling, storage, and treatment so that it does not pollute land and other waters. Natural gas wells and pipelines often have engines to run equipment and compressors, which produce air pollutants and noise.

Natural gas flaring produces CO2, carbon monoxide, sulfur dioxide, nitrogen oxides, and many other compounds, depending on the chemical composition of the natural gas and on how well the natural gas burns in the flare. However, flaring is safer than releasing natural gas into the air and results in lower overall greenhouse gas emissions because CO2 is not as strong a greenhouse gas as methane.

New Technology

New drilling and natural gas recovery technologies significantly reduce the land area that is disturbed to develop oil and gas resources. Horizontal and directional drilling techniques make it possible to produce more natural gas from a single well than in the past, so fewer wells are necessary to develop a natural gas field.

Hydraulic fracturing (commonly called hydrofracking, fracking, or fracing) of shale, sandstone, and carbonate rock formations is opening up large reserves of natural gas that were previously too expensive to develop. Fracking involves pumping liquids under high pressure into a well to fracture the rock, which allows natural gas to escape from the rock. Producing natural gas with this technique has some effects on the environment:

  • The fracturing of wells requires large amounts of water. In some areas of the country, significant use of water for fracking may affect aquatic habitats and the availability of water for other uses.
  • If mismanaged, hydraulic fracturing fluid—which may contain potentially hazardous chemicals—could be released through spills, leaks, faulty well construction, or other exposure pathways. These releases could contaminate surrounding areas.
  • Hydraulic fracturing produces large amounts of wastewater at the surface, which may contain dissolved chemicals and other contaminants that require treatment before disposal or reuse. Because of the quantities of water produced and the complexities inherent in treating some of the wastewater components, proper treatment and disposal of the wastewater is important.
  • According to the U.S. Geological Survey, hydraulic fracturing "...causes small earthquakes, but they are almost always too small to be a safety concern. In addition to natural gas, fracking fluids and formation waters are returned to the surface. These wastewaters are frequently disposed of by injection into deep wells. The injection of wastewater into the subsurface can cause earthquakes that are large enough to be felt and may cause damage."
  • Natural gas could be released to the atmosphere during and after well drilling, and the amounts of these releases are under investigation.

Because a natural gas leak could cause an explosion, strict government regulations and industry standards are necessary to ensure the safe transportation, storage, distribution, and use of natural gas. Because processed natural gas has no odor, natural gas companies add a strong, rotten egg-like smelling substance called mercaptan to natural gas so that people can smell leaks.

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