Horizontal heater treater
Horizontal heater treaters are used in the oil/gas industry to help facilitate oil/water separation by speeding up emulsions separation through applying heat. Heater treaters can be thought of as low pressure, three phase separators equipped with fire tubes. They separate gas from the incoming emulsion and separate the emulsion into a water phase and an oil phase. Heater treaters can also function as a freewater knockout, a heat exchanger, a filter, and as a water wash tank.
The heater treater is normally found downstream of a two-phase separator on a high pressure system. It can be found downstream of the well, a free-water knockout or gun barrel on a low pressure system. Heater treaters are used where the emulsion cannot be broken using just retention, quiescence and chemical demulsifiers. The addition of heat is required to break the emulsion. Heat lowers the viscosity of the oil making it easier for the water to settle. It also creates molecular movement which aids in the coalescing of the water droplets.
Horizontal vs vertical
Heater treaters can be vertical or horizontal in design. Horizontal heater treaters have a much larger oil treating section and they are used to treat heavier crudes where addition settling time is required. Both treaters operate using the same principles.
The incoming emulsion enters the vessel near its top and any gas associated with the emulsion is vented. Any free water immediately drops to the water section where it is discarded. The emulsion flows over the fire tubes where it is heated to the desired temperature as it rises through the heated water section. (The heated water serves to wash the emulsion and to aid in the coalescing of the water droplets.) The emulsion and oil continue to rise into the oil treating section of the vessel where the emulsion breaking process continues. Some treaters are equipped with a "hay" or excelsior section to aid in coalescing the water droplets and to act as a filtering media for removal of solids from the crude oil. The heights of the water and oil columns are controlled by dump valves or by a siphon. The clean oil exits the vessel near the top third of the vessel and the water is drawn off directly under the fire tubes and emulsion distribution pan.
Potential operational problems
Some of the problems which can be encountered that effects the operation of heater treaters are:
- Overloading of the vessel with well fluids does not allow sufficient settling time for complete water removal.
- Operating temperature too low does not provide for complete water removal.
- Malfunctioning water dump valve allowing oil to carryover with the water if the valve hangs open, and allowing water to carryover with the oil if it remains closed.
- A malfunctioning oil dump valve hung in a closed or semi-closed position will allow oil to carryover with the water.