A study conducted for the Texas Environmental Research Commission (TERC) to support the Texas Commission on Environmental Quality (TCEQ) evaluated VOC emission factors and regional emissions of speciated VOCs from oil and natural gas condensate storage tanks at wellhead and gathering sites in East Texas.
Thirty-three tank batteries were used to sample VOC emissions.
Determining VOC Gas Emissions
Storage tank emissions were measured by determining vent gas flow rates and sampling the vent gas for chemical composition. Tank batteries having multiple tanks were sampled through common vent gas gathering pipes located at the tops of the tanks. All vent gas (flash gas) measurements and samplings were conducted at atmospheric pressure and all potential sources of fugitive VOC emissions were sealed before making measurements.
Measuring VOC Gas With Fox Thermal Flow Meters
Flow rates were measured using a Fox Thermal mass flowmeter. The monitoring system consisted of an “instrumentation tube”, a two-inch diameter four-foot-long pipe into which all vent gas was routed so as to flow across the thermal mass flow sensor. The instrument probe of the flowmeter was inserted horizontally at ninety degrees into the instrumentation tube.
Gas flowrate and totalized flowdata were recorded from the Fox Thermal meter. The gas composition was measured using gas chromatography with flame ionization and thermal conductivity detectors. VOC emission factors for vent gas were derived from these field measurements and used to estimate regional emissions from oil and natural gas condensate storage tanks.
Link to Final Report:
VOC Emissions From Oil and Condensate Storage Tanks: Final Report Texas Environmental Research Consortium