Natural Gas Sampling Methods Research
Metering Research Facility

image of Fill and Empty Spot Sampling Method testing in simulated cold ambient conditions

Spot sampling methods are evaluated in cold ambient conditions.

Current Research Goals and Topics of the Natural Gas Sampling Methods Study

The revision of American Petroleum Institute (API) Chapter 14.1, Collecting and Handling of Natural Gas Samples for Custody Transfer, of the API Manual of Petroleum Measurement Standards (MPMS) was completed in 2001. During the revision, the API Working Group compiled a list of unresolved technical issues related to natural gas sampling methodology.

This research project is to address these unresolved technical issues, including the following:

  • The need to accurately determine natural gas hydrocarbon dew points, in order to obtain a representative sample from a natural gas stream without condensation of the heavy components. This required the comparison of equation-of-state models and characterization methods for determining hydrocarbon dew points.
  • The potential for the GPA Fill and Empty sampling method to serve as a potential self-heating method when equipment temperature is below the hydrocarbon dew point.
  • The need to develop a performance verification test protocol for new gas sampling methods.
  • The current state and direction of gas sampling research for saturated natural gas flows and "wet gas" flows (natural gas flows containing small amounts of liquid hydrocarbons).
  • The state-of-the-art of methods for preparing natural gas blends used as calibration standards for chromatography equipment.

Benefit of Natural Gas Sampling Methods Research to Industry

The compositional makeup of a natural gas mixture by means of gas chromatography impacts the determination of both the flow rate and the heating value (the product of which is energy flow rate) of a flowing gas stream. A better understanding of the factors affecting gas sample integrity will ensure that parties who buy and sell natural gas are treated fairly and equitably according to the gas heating value and other composition-dependent properties.

According to Federal Energy Regulatory Commission (FERC) Form 2 data, the unaccounted-for (UAF) gas volume through transmission pipeline networks in the United States averages approximately 0.35%. Industry wide, the quantity of UAF gas is about 150 billion cubic feet per year. If 10% of the UAF gas can be recovered through the application of improved gas sampling standards, the economic impact for custody transfer applications is estimated to be approximately $45 million per year (for gas production, pipeline gathering, and downstream measurement), based on an average gas value of $3 per thousand standard cubic feet.

Related Terminology

flow meter calibrations  •  gas meter  •  gas sampling  •  orifice meter  •  ultrasonic meter  •  natural gas  •  flow conditioner  •  turbine meter  •  flow meter  •  gas quality

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 9 technical divisions.