There are four major types or basic configurations of separators, generally available from manufacturers which are as follows:
1. Vertical
2. Horizontal Single Tube
3. Horizontal Double Tube
4. Spherical
A typical vertical low pressure oil-gas separator with mechanical controls and the features as previously described is illustrated in Figure 9. Figure 9 illustrates a typical vertical high pressure or low pressure oil gas separator with pneumatic controls. The vertical separator has the advantage that it will handle greater slugs of liquid without carry over to the gas outlet, and the action of the liquid level control is not quite as critical, Due to the greater vertical distance between the liquid revel and the gas outlet there is less tendency to revaporize the liquid into the gas phase. Some disadvantages are that it is more difficult and expensive to fabricate and ship this type of separator in skid mounted assemblies, and it takes a larger diameter separator for given gas capacity than a horizontal vessel. From this it can be seen that this type of separator is most often used on fluid streams with row gas-oil ratios. in other words, handling considerably more liquid than gas.
Spherical separators offer an inexpensive and compact vessel arrangement. Figure 13 illustrates a typical low pressure model with mechanical controls. Figure 14 illustrates a similar high pressure spherical oil-gas separator with pneumatic controls. However, this type of vessel has very limited surge place and liquid settling section. The placement and action of the liquid level control in this type of vessel is also very critical.
The horizontal separator has several different advantages particular to this type of construction. Figure l0 illustrates a typical horizontal high pressure or low pressure oil-gas separator with pneumatic controls. The horizontal high pressure double tube separator is illustrated by a typical example shown in Figure 15. The horizontal separator in both the double tube and single tube configuration has several advantages over the vertical separator a8 it is easier to skid mount, less piping is required for field connections, and a smaller diameters required for a given gas capacity. This type of vessel also has a larger interface area between the liquid and gas phases which aids in separation, when gas capacity is a design criteria, the horizontal vessel is not economical in high pressure separators, due to the increased wall thickness required with larger diameters.
However, the liquid level control placement is more critical than in a vertical separator and the surge space is somewhat limited. The double tube separator offers a slight advantage over the single tube is that the liquid section is separated from the gas space, and there is less chance for disturbance of the liquid and re-entrainment of any liquids into the gas phase. However the double tube configuration is more expensive.
Three phase or oil-gas-water separation can be easily accomplished in any type of separator by installing either special internal baffling to construct a water leg or water siphon arrangement or by use of an interface liquid level control. A three phase feature is difficult to install in a spherical due to the limited internal space available. With three phase operation two liquid 1evel controls and two liquid dump valve are required. Figure 11 illustrates a typical vertical high pressure or low pressure separator equipped for oil-gas-water three phase operation. Figure 12 is an illustration of a typical horizontal high pressure or low pressure oil-gas-water separator.
From an evaluation of the advantages and disadvantages of the various types of separators, the horizontal single tube separator has emerged as the one that gives the most efficient operation for initial. investment coat for high pressure gas-distillate wells with high gas-oi1 ratios. For high liquid loadings either low pressure or high pressure vertical type separators should be considered.
