Midstream Oil and Gas
What Is a Compressor Station & How Does It Work?
December 3, 2019 Welcome
Natural gas must travel long distances from the oil & gas production fields to industry users and end customers. While the invention and application of pipeline transportation have made the delivery of natural gas quicker, safer and more cost-effective, several technical challenges arise from this means of distribution.
Gas transported over long distances will experience pressure loss as well as exposure to impurities within the transport channels. To overcome these challenges, natural gas distributors utilize compression stations. These facilities act as sentinels for gas flow measurement that boost dwindling pipeline pressures and facilitate its onward movement.
What Is a Compressor Station
A natural gas compression station is an industrial facility that stabilizes the pressure and flow rate of gases within a pipeline network at optimal levels required to obtain the maximum carrying capacity. A properly operated gas compression facility will efficiently collect gas reaching it, re-pressurize it and channel it to various industries and end processes.
How a Natural Gas Compressor Station Works
Natural gas flowing through a pipeline needs to be pressurized at intervals typically between 40-100 miles to enable it to continue flowing at the desired rate. This routine augmentation in the pipeline pressure is required to correct losses that occur as pressure loss is experienced along the transport line.
Natural gas compressor stations utilize electric motors, natural gas engines and gas turbines to power reciprocating and centrifugal compressors that collect incoming gas, compress it to increase its flow pressure, and channel it to the next station. Depending on the volume of gas to be processed and the distance, the size of the compressor and quantity of compressor stations will vary.
Components of a Gas Compressor Station
It may seem like the compressor is the most critical part of a booster compressor station but there are other key components that are vital to its efficient operation. An ideal gas re-pressurization facility should include the following key components:
Inlet Gas Filtration Units
Natural gas entering a compressor station typically carries minute amounts of impurities. As a first step in the compression process, the incoming gas is channeled through a series of filtration devices (filters, gas scrubbers, gas dehydration units) that remove suspended water vapor, hydrocarbon liquids, dirt, and other particulate contaminants.
While the dried gas is conveyed to the next phase of the compression sequence, the collected hydrocarbon liquids are reinjected into the pipeline downstream of the compressor station.
Prime Mover Units
The prime mover is the compressor driver. Most of the high-pressure natural gas compressor stations use one of three types of compressor/engine systems to achieve gas re-pressurization.
1. Gas Turbine Driven Centrifugal Compressors
A gas turbine compressor station uses a small amount of the gas in the pipeline to fuel a combustion gas turbine known as a mechanical drive. The compressor is normally a centrifugal type and may be a high-speed single-stage or a lower speed multistage compressor. A gas turbine compressor station normally starts around 4000 hp and higher.
2. Electric Type Driven Centrifugal or Reciprocating Compressors
An electric motor compressor station uses generated electricity to power the electric motor driver. The compressor can be a single or multistage centrifugal or reciprocating compressor. Electric motor drivers normally require less maintenance than a gas turbine
3. Reciprocating Engine Driven Compressors
A reciprocating engine compressor station uses a small amount of gas in the pipeline to fuel a gas engine. The compressor is normally a reciprocating type, but can also be a centrifugal compressor. A reciprocating engine compressor station normally ranges up to 4000 hp.
Compressor Station Regulations
Depending on the type, natural gas pipeline compressor station designs may be approved by a state or federal regulatory body. The key groups of pipelines to consider when determining which agency regulates natural gas transport, are gathering lines and interstate transport pipelines.
Compressor Stations Associated with Gathering Lines
Gathering lines are small-sized pipelines (6-20 inches) that collect natural gas from production wells and transport it to processing plants or other natural gas processing/transport stations. These groups of transport channels are regulated by state-run agencies.
Regardless of the pressure at which the natural gas arrives a compression station, regulations mandate re-pressurization between 800-1200 psi before entering interstate pipelines.
Compressor Stations Associated with Interstate Transmission
Interstate transmission lines have larger diameters than gathering lines and transport natural gas across vast distances. Because they cross state boundaries, these pipelines are regulated at a federal level. In the United States, the Federal Energy Regulatory Commission determines the location and operation of all interstate pipeline networks.
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