Midstream Oil and Gas, Pipeline Pump Station, Production Storage & Measurement
What Is a Heater Treater in O&G and How Does It Work?
November 19, 2019 Welcome
Fluid/gas separation is an essential aspect of midstream oil and gas applications, utilized in a wide range of devices and equipment. A well stream flowing from a reservoir contains water molecules that must be removed from the well stream before entering a pipeline for transport to a refinery for processing.
An effective piece of equipment used for this purpose is the heater treater.
What Is a Heater Treater in Oil and Gas?
A heater treater in oil and gas is a 3-phase separator vessel that utilizes heat and mechanical separation devices to facilitate the separation of oil-water emulsions before transporting the dry oil through pipelines.
In this article, we will discuss how heater treaters work, types of heater treaters, and some common applications.
A heater treater consists of four sections that perform the following functions:
- Degassing
- Heating
- Differential oil control
- Coalescing
How a Heater Treater Works
Untreated crude enters the degassing section via an inlet located at the top of the vessel and dry, associated gases are vented into a gas collection line containing a mist extractor. Produced water within the crude drops to the bottom of the vessel and is tapped off from a separate outlet. The emulsion passes into a heating section containing fire tubes that heat it indirectly with heated water. This ‘washes’ the crude mixture, separating the free water and solids.
The treating temperature typically used can be anywhere from 98.6 – 158 °F depending on the crude viscosity. The purpose of heating the oil is to reduce its viscosity and aid the breaking of the emulsion. The oil and emulsion rise over the fire tubes and flow into an oil surge chamber containing a differential float device that regulates the oil level. Some heater treaters have a section containing a filtering medium to screen solid particles out of the oil.
The oil and emulsion flow into the coalescing section through a spreader. This section comprises an electrostatic device that passes alternating current through the emulsion to induce droplet coalescence. As the water molecules separate from the emulsion, they collide and form larger droplets that settle to the bottom of the tank under the force of gravity. The dry oil is tapped via a separate outlet at the top of the tank.
Heater treaters are available in vertical or horizontal orientations. The main difference between a vertical heater treater and a horizontal heater treater for oil and gas is the duration for which the liquid stays in the vessel. The cycle time in horizontal heater treaters is usually longer than that in the vertical orientation.
Let’s look at the two configurations in closer detail.
Horizontal Heater Treater
The orientation of a horizontal heater treater is a cylindrical vessel lying on its side. Horizontal heater treaters have the same basic operation as vertical treaters but have a larger section for treating the crude.
A key benefit of this orientation is that the vessel can handle higher volumes of fluid and heavier crudes that require longer retention periods for separation. Horizontal heater treaters can treat emulsions of any API gravity with high water content.
Vertical Heater Treater
Vertical heater treaters are cylindrical vessels in an upright position. They have a smaller crude treating volume than the horizontal type, making them ideal for space-constrained applications. These vessels are better suited for separating lighter crudes that require shorter retention periods. Vertical heater treaters can treat emulsions having API gravity up to 27 and low water content.
Challenges with Using Heater Treaters for Separation
Some common issues that negatively impact the efficiency of heater treaters include inadequate operating temperatures, faulty water dump valves, faulty oil dump valves, and overloading of the vessel with well fluids. These conditions can lead to partial water removal from the emulsion.
Common Heater Treater Applications
Horizontal and vertical heater treaters are used extensively in the oil and gas industry to separate produced water and associated gas from oil-water emulsions. They are useful for separating emulsions that cannot be broken down with simple retention and chemical demulsification.
Heater treaters operate at low pressures and are usually located downstream of an oil/gas well or just before the oil sales storage tanks in a treatment unit.
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