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Interstate Pipeline Gas Quality Primer

This primer provides an overview of the basis for gas quality specifications and their development in the interstate pipeline business. It discusses the criteria, trade-offs, and data collection methods, as well as the applicability of gas quality specifications. The primer concludes with key considerations and limitations of gas quality data.

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Interstate Pipeline Gas Quality Primer

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  1. Interstate Pipeline Gas Quality Primer Business Practices Subcommittee June 15-16, 2004 PIPELINE SEGMENT Wholesale Gas Quadrant North American Energy Standards Board

  2. OVERVIEW • Basis for Gas Quality Specifications • Development • Criteria • Trade-offs • Gas Quality Data • Collection • Availability • Usage • Gas Quality Specifications/Applicability • Components • Understanding • Conclusions

  3. Basis for Gas Quality Specifications Industry Development • First pipelines (1920s – 1930s) were regional • Few pipe-to-pipe deliveries • Specific supplies delivered to specific markets • Little concern about variations in supply mix • Each system developed criteria for specific safety and market requirements • End-use equipment designed and installed based on specific supply availability • Subsequent development of pipeline grid (1970s-1980s) • Additional quality criteria applied to specific systems • Additional pipe-to-pipe deliveries • Minimum coordination of quality specifications at interconnects

  4. Basis for Gas Quality Specifications • Gas quality specifications have been developed based on: • Operational Safety • Operational Efficiency • Supply availability • Market requirements • Processing responsibilities • Deliberate trade-offs between economics and requirements of production, transportation and end-use parameters

  5. Basis for Gas Quality Specifications • Operational Safety • Limitations on harmful components • H2S – highly poisonous • Sulfur – by-products during combustion • Specifications to control damaging properties • Water/water vapor content – corrosion • Oxygen – corrosion • Carbon Dioxide - corrosion

  6. Basis for Gas Quality Specifications • Operational Efficiency • Btu parameters • Throughput capacity • Specific Gravity • Gas flow efficiency • Hydrocarbon Liquefiables • Capacity restrictions • Inerts • Btu impact • Emissions concerns

  7. Basis for Gas Quality Specifications Gas Quality Trade-offs • After assuring safety, other quality criteria often established to optimize availability of supplies, market requirements and economics

  8. Gas Quality Data • Gas Quality Data Collection • Electronic evaluation (Chromatograph and other instrumentation) • Relatively expensive • Often telemetered • May not be operationally feasible (power/radio) • Sampling – physical evaluation • Continuous sample • Gas stream tested for a specified period • Spot sample • Gas stream tested at a point in time • Other Sample • Random sample/sample period • Equipment in place is pertinent to pipeline and customer requirements • Data requirements may be contract driven

  9. Gas Quality Data • Data availability • Location • Electronic measurement (EMS) vs. charts • Size of meter • Frequency of flow • Support for installation (power, transmission) • SCADA • Operational data • Not billing quality information • Timing • Measurement parameters • Data availability • Reporting frequency • Adjustments • Operational vs. Billing Quality • Not all data is available and/or monitored daily

  10. Gas Quality Data • Quality Data Usage • Real Time vs. Periodic Reporting • Electronic reporting • Sampling frequency • Proprietary Issues • Operator-to-operator specific performance issues • Within Tariff tolerance is criteria for other performance • Receipt-to-delivery relationships • Blending • Timing of quality readings (transients) • Delivered quality • Specific supply quality may not be an issue

  11. Gas Quality Specifications/Applicability • Typical Pipeline Gas Quality Components • Btu Content (Minimum/Maximum limits) • Hydrogen Sulfide (H2S) • Total Sulfur (S) • Nitrogen (N) • Carbon Dioxide (CO2) • Oxygen (O2) • Water and/or Water Vapor • Hydrocarbon Liquefiables • Temperature • Total Inerts • Dust, Gum, Dirt • Other • Burnability (HHV, HV, Input Factor, Wobbe) • Mercaptans • Not all applicable to all pipelines

  12. Gas Quality Specifications/Applicability • Context of Gas Quality Data • Transient information • Upstream information may not be a predictor of delivery quality • Level of data availability/presentation • Pooling/Blending • Reticulated systems (variable direction flows) • Downstream blended data may be more indicative of gas quality performance

  13. Conclusions • Understanding the context of quality information is critical for its use • Not all gas quality information is captured at all points • Gas quality at any point is a mix of input qualities/quantities and existing line pack • Real-time information is probably not feasible for posting • Daily data (if electronic) may be best available information • Blended information (24 hours) • May not be reflective of future flows • May not be available at all locations

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