The purification and refinement process for natural gas starts at the wellhead. After the gas is extracted from the well, it flows into inlet separators. These separators are large drums designed to separate wellstreams into their individual components. They are commonly designed to separate two-phase (gas/liquid) or three-phase (gas/crude/water) wellstreams. Separators are also classified according to horizontal or vertical configuration, operating pressure, turbulent or laminar flow, and test or production separation.
In this blog series, based on the Magnetrol® brochure on natural gas processing, we will explore level measurement solutions for a variety of applications, from separators to flare knock-out drums. This blog post examines the challenges in measuring the level of inlet separators and discusses instrumentation that can provide more reliable measurement.
Types of Separators
There are two principal types of separators, vertical and horizontal.
Vertical: Vertical separators can accommodate large surges of liquids. They are well suited for high sediment loads—conical bottoms are sometimes attached for large sediment deposits. Vertical separators are preferred when wellstreams have large liquid-to-gas ratios. These separators occupy less floor space than horizontal types and are often found on offshore platforms where floor space is at a premium.
Horizontal: These separators are well-suited for three-phase separation because of their large interfacial area between the two liquid phases. Horizontal types are preferred when wellstreams have high gas-to-oil ratios, when wellstream flow is more or less constant, and when liquid surges are insignificant. These separators also have a much greater gas/liquid interface area, which aids in the release of solution gas and in the reduction of foaming.
Level Measurement Challenges
Interface level measurement will actuate a valve to adjust vessel level. An emulsion layer along the oil/water interface can contaminate the oil with water or the water with oil. Foaming along the gas/liquid interface, if entrained, can cause liquid carryover or gas blowby. Instrumentation must be sensitive to the interface and able to easily detect these possible issues.
Level Measurement Solutions
MAGNETROL has produced level measurement solutions for inlet separators:
- For point level:
Series 3 float-actuated external cage level switch or Thermatel® Model TD1/TD2 switch
- For continuous level and interface level:
Eclipse® Model 706 guided wave radar transmitter; Jupiter® JM4 magnetostrictive level transmitter; or E3 Modulevel® displacer transmitter
- For visual indication:
Atlas or Aurora® magnetic level indicators
For more information on level measurement solutions for inlet separators and other natural gas processing applications, download the natural gas processing brochure.