Natural gas is an important part of the world’s energy supply. From feedstock for production processes to generating electrical power, the transportation, distribution, storage, and processing of natural gas has a global impact.
Natural gas must meet specific requirements as it relates to heating value, hydrocarbon dew point, and the concentration of various contaminants. The quality of natural gas can be impacted by contaminants, such as water vapor, sulfur-based compounds, heavier hydrocarbons, and carbon dioxide. These contaminants adversely affect the natural gas heating content, promote the formation of acids that damage mechanical infrastructure, and facilitate hydrate formation, which limits gas flow in pipelines. All of these can result in damage to key components, increase maintenance costs, and cause unplanned downtime.
Applications across the natural gas value chain include:
Natural Gas Dehydration
Most operators of natural gas pipelines establish a tariff or contract limit on the moisture content allowed in a pipeline. Moisture or water vapor (H₂O) in natural gas promotes the formation of hydrates and corrosive acids, causes freezing, increases gas transportation and compression costs, and reduces the heating content of the natural gas.
Natural Gas Sweetening
Hydrogen sulfide (H₂S) and carbon dioxide (CO₂) promote corrosion and cause stress cracking in the pipelines. Additionally, H₂S is a highly toxic and flammable compound that is a continuous risk for personnel safety. H2S and CO2 must be removed from the natural gas, in a process referred to as natural gas sweetening, which reduces the risk of being “locked-out” of the pipeline network if concentrations exceed the tariff or contact limit.
Transmission Pipelines & Custody Transfer
A custody transfer measurement is considered a fiscal measurement and is critically important to understand the heating value of the natural gas and the amount of gas being transferred. Some key considerations during custody transfer include:
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Ensuring gas quality compliance with tariff or contract limits for moisture, sulfur-based compounds, hydrocarbon dew point temperature, and specific gravity.
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Accurately measuring gas composition, heating value, and relative density to comply with contractual requirements for fiscal accounting.
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Protecting the pipeline from increased pressure drop, reduction in line capacity, and damage to equipment.
Underground Storage
When natural gas is not immediately needed, or if production exceeds demand, the gas is stored underground. Measurements of H2O and H2S ensure that any storage gas inventory already present is not contaminated, and that the storage facility is not adversely affected. Some key considerations when measuring gas stored underground are:
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High concentrations of either H₂O or H₂S can contaminate the underground storage facility.
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High storage pressures can cause condensation.
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The gas must meet tariff or contract requirements for the transmission pipeline during extraction.
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Reliable, accurate analysis of gas quality is important during peak demand periods.
Hydrocarbon Processing (LPG & NGL Recovery)
Natural gas contains liquids that must be removed following extraction. Key measurement considerations include monitoring and optimizing the dehydration process to prevent “breakthrough” in the molecular sieve dryer, protecting the expansion turbine from damage, and ensuring final product quality specifications are met.
Liquified Natural Gas Production
When natural gas cannot be transported in its gaseous state in a pipeline, the gas is converted to a liquid, called liquefied natural gas (LNG), in a process called liquefaction. Key considerations during this process include monitoring and optimizing the dehydration process to prevent “breakthrough” in the molecular sieve dryer, preventing formation of ice during the refrigeration process, and preventing formation of corrosive acids due to presence of moisture with H₂S and CO₂.
For more information click here to view our Natural Gas Solutions brochure.