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High And Low Pressure Gas Systems In Oil & Gas Production

Many wells produce some amount of natural gas along with crude oil. Others may produce mostly or only natural gas. Whenever there is enough gas coming from the well to be worth collecting and selling it, additional equipment and vessels need to be added to the tank battery and wellhead. All of the equipment intended for handling gas production together is called the gas system. It begins at the separator, where gas breaks out from liquid well products.Get more news about high and low pressure components wholesaler,you can vist our website!

Pressure is an important consideration in any tank battery. It forces fluid and gas through the different vessels, and helps prevents loss through evaporation. Pressure is controlled by valves, both in the gas outlet line and the water and oil outlet lines. The oil and water lines use diaphragm controlled valves to maintain backpressure. The gas line will also use a diaphragm backpressure valve. Diaphragm valves have an arrangement that uses a spring and bolt on the top to adjust the dump pressure.

Fluids can only flow from a higher pressure to a lower pressure vessel, so the separator will have the highest pressure of all the vessels in the tank battery, and the stock tanks will have the lowest. This pressure balance is controlled by the gas system.

Wells are usually tested regularly each month. Part of that testing is a measurement of the gas pressure and volume that is being produced. The well will typically be produced through to the tank battery so that measurements can be taken by a meter, like the one shown in Figure 3.

The High Pressure System
A gas system can be divided roughly into a high pressure system and a low pressure system. The high pressure system is not truly at a high pressure, particularly when compared to pressures downhole; the separator may be the only vessel that is part of the high pressure system. However, the separator can have a pressure of between 20 and 50 psi, which is enough to require caution.

In some cases, particularly with marginal wells, the gas produced may be a very small amount. The casing may just be left open to vent whatever gas is produced. Enough gas may remain in the fluid, however, that a separator may still be required. Other vessels that might be considered part of the high pressure system include any heater-treaters or wash tanks that may be under more than a few pounds of pressure.
The Low Pressure System
The low pressure system is largely made up of atmospheric tanks, such as stock tanks. Stock tanks will normally have a few ounces to a few pounds of backpressure, which helps to prevent loss by evaporation. Gas will usually flow out of the tanks’ gas outlets and from there to the vapor recovery unit, with a small amount of pressure held by a valve. Even though the pressure is quite low, a safety release valve is still necessary. A simple option that is popular is to use a length of L shaped pipe. This can be used with a diaphragm valve as a safety valve if pressure should build in the vessel.