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What is Produced Water?

Formation Water or Produced Water?

Produced water is located in subsurface formations or naturally occurring rocks permeated with fluids such as water, oil, or gas. This water is frequently referred to as "connate water" or "formation water" and becomes produced water when the reservoir is produced and these fluids are brought to the surface. Produced water is any water that is present in a reservoir with the hydrocarbon resource and is produced to the surface with the crude oil or natural gas. It is believed that the rock in most oil-bearing formations was completely saturated with water prior to the invasion and trapping of petroleum. The less dense hydrocarbons migrated to trap locations, displacing some of the water from the formation in becoming hydrocarbon reservoirs. Thus, reservoir rocks normally contain both petroleum hydrocarbons (liquid and gas) and water. Sources of this may include flow from above or below the hydrocarbon zone, flow from within the hydrocarbon zone, or flow from injected fluids and additives resulting from production activities.

When industry produces hydrocarbons, they are brought to the surface as a fluid mixture. The composition of this fluid is dependent on whether the production involved either crude oil or natural gas, and generally includes a mixture of either liquid or gaseous hydrocarbons, dissolved or suspended solids, other solids such as sand or silt, and injected fluids and additives that may have been placed in the formation as a result of exploration and production activities.

This is by far the largest volume byproduct or waste stream associated with oil and gas production. Management of it presents challenges and costs to operators, as it has often been identified as a major constraint in the production of hydrocarbons. The costs of lifting, separating, handling, treating, and disposing of this contamination are substantial. In addition to the economic burden it imposes, it can also directly reduce hydrocarbon production.

Environmental Importance of Treatment

As the US expands the development of fossil energy resources to meet our ever-increasing demand for energy, we must address the environmental issues associated with this development. For every barrel of oil, approximately 10 barrels of contamination can be generated; presently we generate over 5 billion gallons a day. It is common to ask how it might be treated and put to some beneficial use, instead of just disposing of it. In the past, it was handled as a waste and reinjected, often at significant cost to the producer. As the US demand for freshwater outstrips available supplies, we are increasingly turning to treatment technology to create freshwater. Because of the large volumes of brackish being generated, the treatment of this is increasingly being looked at as a way to supplement our limited freshwater resources in many parts of the country.

The many chemical constituents can be found either individually or collectively in high concentrations, and can present a threat to aquatic life when they are discharged or to crops when used for irrigation. It can also have different potential impacts depending on where it is discharged. For example, discharges to small streams are likely to have a larger environmental impact than discharges made to the open ocean by virtue of the dilution that takes place following discharge. Regulatory agencies have recognized the potential impacts that discharges can have on the environment and have prohibited discharges in most onshore or near-shore locations.