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The Petroleum Industry and the Treatment of Produced Water
The use of ground water by the petroleum sector can be considered as a new potential procurement of water in certain regions where natural water levels are low and where careful treatment of the produced water allows for its safe use.
A short explanation of the process of petroleum extraction in relation to produced water
During the production of oil either from conventional or unconventional sources, extraction processes generate large quantities of ground water that come in contact with the various drilling fluids and hydrocarbons, and other contaminants naturally present in the substrate (salt for example) resulting in water contamination. This water is known as produced water.
Produced water if properly treated can be used for irrigation, livestock watering, aquifer storage, stream- flow augmentation, municipal and industrial uses.
The quantity and composition of produced water varies depending on the geological formation, notably the formations of conventional and non-conventional petroleum. In general the conventional reserves pump more produced water than non-conventional reservoirs such as gas.
The geological formations of conventional oil and gas are composed of localized deposits while the remainder of the formation is filled with formation water. During the extraction of this type of geological formation vertical drilling allows oil to rise to the surface, followed by water from impermeable layers of the underground reservoir.
Since the formation water exists naturally in porous aquifers, the quality of the water depends mainly on the geographical location of the hydrocarbons, and chemical and biological properties of the sedimentary formation. After mining, the produced water contains contaminants which are mainly due to its direct contact with hydrocarbons.
The composition of sedimentary formations of non-conventional sources such as oil shale, differ from conventional sources. The amount of produced water generated by this type of source is lower than conventional sources since this type of reservoir is normally more compact. Shale oil is a lighter oil type derived from sedimentary rocks having the distinction of being from tighter reservoir formations.
This type of oil can be trapped in shale, sandstone and carbonate rock formations with very low permeability. Contrary to conventional reservoirs where oil and gas are relatively mobile, shale oil stays where it was originally formed. Thus, removing shale oil requires high pressure to fracture the rock in order to release the shale oil. The pressure is created by injecting a fracturing fluid, which in most cases is a mixture of fresh water (90%), sand and additives that create cracks in the shale at various locations, liberating the oil so it can be pumped up to the surface. Formation water is mixed with fracturing fluid and the hydrocarbons, thus forming produced water.
Treatment of Produced Water and Recommended Products
Before the release of produced water into the environment it is necessary to treat it properly or dispose of it safely. The common practice is to transfer the water by injecting it into deep wells drilled by formations designed for this use. However, proper treatment of this water presents a solution to the issue of scarcity of water reserves in certain regions. Indeed, the valuation of the largest waste oil extraction industry is produced water that can meet water demands at many levels. By transferring produced water to retention basins, treatment of the produced water with aeration and bio-augmentation (adding beneficial bacteria) can occur, thereby creating a much needed safe water resource from produced water.
As for the management of tailings ponds, our expertise in managing water quality can help offer solutions to achieve water quality standards from hydrocarbon reserves for various applications. Aeration with industrial diffuser OctoAir™-10 or the Bubble Tubing® allows a high oxygen transfer rate *. These diffusers optimize oxygenation of water to reduce and decompose the organic matter of the polluting load of the water while promoting the beneficial activity of added aerobic bacteria. These aeration systems can be used all year round.
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