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Tribal Energy and Environmental Information Clearinghouse: Environmental resources for tribal energy development
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Oil or Gas Drilling/Development Phase: Resource Requirements and Impact Sources

Potential impacts from the drilling and development of an oil or gas field affect much of the project area. Most impacts from drilling and development are temporary in nature, but much of the well site and ancillary facility areas would be altered for the full production period.

The following describes the factors that could affect whether environmental impacts could occur during the drilling/development phase.

Requirements and Impact Sources

  • Acreage – An average oil or gas field has about 4 to 16 wells per square mile. Some coal bed methane fields have wells located every 20 acres, but typical gas methane well spacing varies from one per 40 acres to 320 acres. An individual well pad would occupy less than 5 acres; however, up to 40 acres/well could be disturbed depending upon the length of access roads, pipelines, size of equipment and equipment storage yards, number of wells being drilled from a pad, and other factors associated with the well. Horizontal well drilling techniques can minimize surface disturbance. For example six to eight horizontal wells on a multi-well drill pad can access the same shale gas reservoir volume as sixteen vertical wells.
  • Emissions – Dust emissions would be produced during clearing, grading, excavation, and blasting; also vehicular and well drilling equipment emissions; and volatile organic compounds (VOCs) from storage and use of equipment fuels. Well drilling emissions could include natural gas (including methane, a greenhouse gas), other VOCs, polycyclic aromatic hydrocarbons (PAHs), BTEX (benzene, toluene, ethylbenzene, and xylenes), carbon dioxide, carbon monoxide, and hydrogen sulfide.
  • Waste Generation – Industrial wastes would be produced that are routinely associated with industrial facility construction activities (e.g., waste oils, lubricants, and coolants from the on-site maintenance of construction vehicles and equipment, spent solvents, cleaning agents, paints, and other corrosion control coatings applied to structures, sanitary wastes, and small amounts of wastewaters from cleaning operations). A potentially large quantity of solid waste would include woody vegetation and miscellaneous wastes associated with site clearing and assembly activities. The main wastes associated with oil and gas production are drilling-waste fluids (muds) – up to 300,000 gallons per day, drilling-waste solids, produced water, and VOCs. Other assorted wastes include sanitary wastes, dispersants, corrosion inhibitors, surfactants, flocculating agents, concrete, casing, and paraffins.
  • Water Needs – Water would be required for dust control and for making concrete and for use in drilling fluids. Small amounts of water would be needed for potable use and for cleaning operations throughout construction and drilling. A supply of water in case of accidental fire would also be required. Hundreds of thousands to millions of gallons of water could be required to drill and complete a well. About 3 million gallons or more of water could be required for hydraulic fracturing of the formation. Water recycling employed to process the drilling fluid can reduce water needs by 50 to 65%.
  • Workforce – About 800 worker-days could be required to construct a well (including workers needed to construct and drill the well and construct access roads and pipelines). On average, about five people, mostly equipment operators, would work on the construction of an individual well pad. Drilling activities for an individual well would require about 12 workers and take about 13 days for a shallow well and up to 46 days for a deep well. Well completion would require about 15 workers and would take 29 to 54 days, depending on depth of the well and number of completion zones. About 10 to 25 construction and supply-related workers would be needed to install new sections of a pipeline gathering system. Access roads would take about one day to construct 1.5 mi of road (on flat areas) to 2 to 3 days for 1.5 mi on steep terrain. About five people would be needed to construct access roads (10 to 25 workers to work in several crews for trunk roads to multiple well pads).
  • Time – Construction of a well pad, access roads, gathering pipelines, and other ancillary facilities could take more than 20 days to construct. It could take about three months to drill an individual well.
  • Utility Requirements – Electricity needed to power the drill rigs would probably be supplied by electric power generators that run on diesel fuel.