An oil and gas separator generally includes the following essential components and features: Separators work on the principle that the three components have different densities, which allows them to stratify when moving slowly with gas on top, water on the bottom and oil in the middle.
In cold climates, freezing will likely cause less trouble in the monotube unit because the liquid is usually in close contact with the warm stream of gas flowing through the separator.
The monotube design normally has a lower silhouette than the dual-tube unit, and it is easier to stack them for multiple-stage separation on offshore platforms where space is limited.
In such cases, the separator vessel affords only an "enlargement" to permit gas to ascend to one outlet and liquid to descend to another.
The physical and chemical characteristics of the oil and its conditions of pressure and temperature determine the amount of gas it will contain in solution.
The volume of gas that an oil and gas separator will remove from crude oil is dependent on (1) physical and chemical characteristics of the crude, (2) operating pressure, (3) operating temperature, (4) rate of throughput, (5) size and configuration of the separator, and (6) other factors.
Valves on the oil and water outlets are controlled to ensure the interfaces are kept at their optimum levels for separation to occur.
In some instances it is preferable to separate and to remove water from the well fluid before it flows through pressure reductions, such as those caused by chokes and valves.
This liquid seal prevents loss of gas with the oil and requires the use of a liquid-level controller and a valve.
Effective oil-gas separation is important not only to ensure that the required export quality is achieved but also to prevent problems in downstream process equipment and compressors.
More recently new devices with higher gas-handling have been developed which have enabled potential reduction in the scrubber vessel size.
These systems are based on centrifugal and turbine technology and have additional advantages in that they are compact and motion insensitive, hence ideal for floating production facilities.
At standard conditions of pressure and temperature, the droplets of liquid hydrocarbon may have a density 400 to 1,600 times that of natural gas.
For this reason, it is desirable to operate oil and gas separators at as low a pressure as is consistent with other process variables, conditions, and requirements.
This is largely overcome by placing vertical quieting baffles which should extend from the bottom of the separator to above the outlet.
A spreader plate that disperses the oil into small streams or rivulets increases the effectiveness of the heated-water bath.
A properly shaped and sized vortex will allow the gas to ascend while the liquid flows downward to the bottom of the unit.
The purpose of the study was to investigate the complex multiphase hydrodynamic flow behaviour in a three-phase oil and gas separator.
The simulation time for the experiment was 20 seconds with the oil specific gravity as 0.885, and the separator lower part length and diameter were 4-ft and 3-inches respectively.
The first set of experiment became a basis through which detailed investigations were used to carry out and to conduct similar simulation studies for different flow velocities and other operating conditions as well.
[13] Calibration can be defined as the process of referencing signals of known quantity that has been predetermined to suit the range of measurements required.
However, according to Ting et al (1989),[14] transfer meters have been proven to be less accurate if the operating conditions are different from its original calibrated points.
In the U.S., master meters are often calibrated at a flow lab that has been certified by the National Institute of Standards and Technology, (NIST).
However, there is a general belief in the industry that the second method which involves the gravimetric weighing of the amount of fluid (liquid or gas) that actually flows through the meter into or out of a container during the calibration procedure is the most ideal method for measuring the actual amount of flow.
Apparently, the weighing scale used for this method also has to be traceable to the National Institute of Standards and Technology (NIST) as well.
ESD valves typically stay in open position for months or years awaiting a command signal to operate.
As a result, many operators find their separator no longer able to meet the required oil and water effluent standards, or experience high liquid carry-over in the gas according to Power et al (1990).
[20] Some operational maintenance and considerations are discussed below: In refineries and processing plants, it is normal practice to inspect all pressure vessels and piping periodically for corrosion and erosion.
In the oil fields, this practice is not generally followed (they are inspected at a predetermined frequency, normally decided by an RBI assessment) and equipment is replaced only after actual failure.
Steam coils can be installed in the liquid section of oil and gas separators to melt hydrates that may form there.