The Hydraulic Fracturing Water Cycle

EPA's study will look at potential impacts of hydraulic fracturing at each stage of the Hydraulic Fracturing Water Cycle.

Click on the image below to learn more about the Hydraulic Fracturing Water Cycle.

The hydraulic fracturing water cycle.  Please click on the image for an explanation of each step.1. Water AcquisitionNatural gas flows from fissures into well.2. Chemical Mixing3. Well Injection4. Flowback and Produced Water (Wastewater)5. Wastewater Treatment and Waste Disposal
 

Stage 1: Water Acquisition 1

  • Large volumes of water are withdrawn from ground water 2and surface water 3resources to be used in the hydraulic fracturing process.
  • Potential Impacts on Drinking Water Resources
    • Change in the quantity of water available for drinking
    • Change in drinking water quality

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Stage 2: Chemical Mixing

  • Once delivered to the well site, the acquired water is combined with chemical additives 4and proppant 5to make the hydraulic fracturing fluid.
  • Potential Impacts on Drinking Water Resources
    • Release to surface and ground water through on-site spills and/or leaks

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Stage 3: Well Injection

  • Pressurized hydraulic fracturing fluid is injected into the well, creating cracks in the geological formation that allow oil or gas to escape through the well to be collected at the surface.
  • Potential Impacts on Drinking Water Resources
    • Release of hydraulic fracturing fluids to ground water due to inadequate well construction or operation
    • Movement of hydraulic fracturing fluids from the target formation to drinking water aquifers through local man-made or natural features (e.g., abandoned wells and existing faults)
    • Movement into drinking water aquifers of natural substances found underground, such as metals or radioactive materials, which are mobilized during hydraulic fracturing activities

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Stage 4: Flowback 6and Produced Water 7(Hydraulic Fracturing Wastewaters)

  • When pressure in the well is released, hydraulic fracturing fluid, formation water, and natural gas begin to flow back up the well. This combination of fluids, containing hydraulic fracturing chemical additives and naturally occurring substances, must be stored on-site—typically in tanks or pits—before treatment, recycling, or disposal.
  • Potential Impacts on Drinking Water Resources
    • Release to surface or ground water through spills or leakage from on-site storage

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Stage 5: Wastewater Treatment and Waste Disposal

  • Wastewater is dealt with in one of several ways, including but not limited to: disposal by underground injection, treatment followed by disposal to surface water bodies, or recycling (with or without treatment) for use in future hydraulic fracturing operations.
  • Potential Impacts on Drinking Water Resources
    • Contaminants reaching drinking water due to surface water discharge and inadequate treatment of wastewater
    • Byproducts formed at drinking water treatment facilities by reaction of hydraulic fracturing contaminants with disinfectants

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1Recently, some companies have begun recycling wastewater from previous hydraulic fracturing activities, rather than acquiring water from ground or surface resources.

2Ground water is the supply of fresh water found beneath the Earth’s surface, usually in aquifers, which supply wells and springs. It provides a major source of drinking water.

3Surface water resources include any water naturally open to the atmosphere, such as rivers, lakes, reservoirs, ponds, streams, impoundments, seas, estuaries, etc. It provides a major source of drinking water.

4Chemical additives are used for a variety of purposes (see examples in Table 4 on page 29 of the hydraulic fracturing Study Plan (PDF) ). A list of publicly known chemical additives found in hydraulic fracturing fluids is provided in Appendix E, Table E1 of the hydraulic fracturing Study Plan (PDF) .

5Proppant is a granular substance such as sand that is used to keep the underground cracks open once the hydraulic fracturing fluid is withdrawn.

6After the hydraulic fracturing procedure is completed and pressure is released, the direction of fluid flow reverses, and water and excess proppant flow up through the wellbore to the surface. The water that returns to the surface is commonly referred to as “flowback.”

7After the drilling and fracturing of the well are completed, water is produced along with the natural gas. Some of this water is returned fracturing fluid and some is natural formation water. These produced waters move back through the wellhead with the gas.