In the oil industry, waterflooding or water injection is where water is injected into an oil field, usually to increase pressure and thus stimulate production. Water injection wells can be found both on land and offshore, to improve oil recovery from existing reservoirs.
Water is injected to support reservoir pressure (also known as a voidage substitute), and also to sweep or remove oil from the reservoir, and push it toward the well.
Usually only 30% of the oil in the reservoir can be extracted, but the water injection increases the percentage (known as the recovery factor) and maintains the reservoir production rate for a longer period of time.
Waterflooding started accidentally in Pithole, Pennsylvania in 1865. Waterflooding became common in Pennsylvania in the 1880s.
Video Water injection (oil production)
Injected water source
Any bulk water source can be used for injection. The following water sources are used for oil recovery:
Water produced is often used as a liquid injection. This reduces the potential for formation damage due to incompatible fluids, although the risk of scaling or corrosion of injection or tubing flowlines remains. In addition, the water produced, contaminated with hydrocarbons and solids, must be disposed of in certain ways, and discharges into the sea or river will require a level of water flow cleaning first. However, the processing required to make water produced according to reinjection may be equally expensive.
Since the volume of water produced is never enough to replace all production volumes (oil and gas, other than water), additional "make-up" water should be provided. Mixing water from different sources exacerbates the risk of scaling.
Sea water is clearly the most convenient source for offshore production facilities, and may be pumped on shore for use in the fields. As much as possible, the water intake is placed at considerable depth to reduce algae concentration; However, filtration, deoxygenation and biociding are generally required.
Water aquifers of water formations other than oil reservoirs, but in the same structure, have the advantage of purity if available.
River water will always require filtering and biociding before the injection.
Maps Water injection (oil production)
Filters
Filters should clean water and remove any impurities, such as shells and algae. The typical filtration is 2 micrometers, but it depends heavily on reservoir requirements. The filter is very smooth so it does not block the pores of the reservoir. Sand filter is a common filtration technology used to remove dense impurities from water. Sand filters have different beds with different sizes of sand grains. The seawater crosses the sand layer first to the roughest to the best and cleans the filter, the process is reversed. After the water is filtered, proceed to fill the de-oxygenation tower. Large sand filters, heavy, have some spilled mineral particles and need chemicals to improve water quality. A more sophisticated approach is to use automatic self-backing automatic filter (suction scanning) because it does not have the disadvantages of sand filters.
The importance of proper water treatment is often underestimated by oil companies and engineering companies. Particularly with rivers, and seawater, the quality of intake water can vary greatly (algae bloom in spring, storms and currents that stir sediment from the seafloor) which will have a significant impact on the performance of water treatment facilities. If not handled properly, water injection may not work. This results in poor water quality, reservoir bioclogging and loss of oil production.
De-oxygenation
Oxygen must be removed from water because it increases the corrosion and growth of certain bacteria. The bacterial growth in the reservoir can produce toxic hydrogen sulfide, the source of serious production problems, and blocking the pores in the rock.
A deoxygenation tower brings injectable water into contact with the flow of dry gas (gas is always available in oil fields). Filtered water falls into the de-oxygenation tower, splashing onto a series of trays, causing dissolved oxygen to be lost to the gas stream.
An alternative method, also used as a backup for deoxygenation towers, is to add oxygen cleaning agents such as sodium bisulphite and ammonium bisulfit.
Another option is to use membrane contactors. Membrane contactors carry water into contact with an inert gas stream, such as nitrogen, to remove dissolved oxygen. Membrane contactors have advantages as lower and compact weights that allow the design of smaller systems.
Water injection pump
High pressure high-flow water injection pumps are placed near de-oxygenation towers and reinforcing pumps. They fill the bottom of the reservoir with filtered water to push the oil into the well like a piston. Injection results are not fast, it takes time.
Water injection is used to prevent low pressure in the reservoir. Water replaces the oil that has been taken, maintaining the same level of production and pressure in the long run.
Resources and notes
- "Billions of New In Oil" Popular Mechanics , March 1933 - i.e. article on water injection discovery for oil recovery
- Water injection
- Calculation of Waterflood Prediction Calculations
Source of the article : Wikipedia
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