Oil production plant
An oil production plant (sometimes called an oil terminal) is a facility which performs processing of production fluids from oil wells in order to separate out key components and prepare them for export. This is distinct from an oil depot, which do not have processing facilities.
Typical production fluids are a mixture of oil, gas and produced water. Many permanent offshore platforms have full oil production facilities onboard. Smaller platforms and subsea wells must export raw production fluid to the nearest production facility, which may be on a nearby offshore processing platform or an onshore terminal.
Process
The production plant is said to begin after the production wing valve on the oil well. The product from each well is piped through the choke valve, which regulates the rate of flow. The flowlines are gathered in a manifold and routed into a separator, which will gravity separate the three components. Once the oil has been separated from the gas and produced water, it is usually routed to a coalescer before being metered and pumped to the onshore terminal.
The produced water is often routed to a hydrocyclone to remove entrained oil and solids and then either re-injected into the reservoir or dumped overboard depending on the circumstances and cleanliness of the water. The associated gas is initially dubbed "wet gas" as it is saturated with water and liquid alkanes. The gas is typically routed through scrubbers, compressors and coolers which will remove the bulk of the liquids. This "dry gas" may be exported, re-injected into the reservoir, used for gas lift, flared or used as fuel for the installation's power generators.
Onshore terminals generally have fired heaters followed by separators and coalescers to stabilise the crude and remove any produced water not separated offshore. Onshore separators tend to operate at a lower pressure than the offshore separators and so more gas is evolved. The associated gas is generally compressed, dew-pointed and exported via a dedicated pipeline. If gas export is uneconomical then it may be flared. Onshore terminals frequently have large crude oil storage tanks to allow offshore production to continue if the export route becomes unavailable. Export to the refinery is either by pipeline or tanker.
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