Optical Technology to Quantify and Mitigate Methane Emissions from Casing Gas Vents and Liquid Storage Tanks

Lead Proponent

Carleton University

Project Background

The objective of this project was to develop and field test a novel optical-based technology for measuring key sources of vented methane in the oil and gas sector. Venting of casing gas during heavy oil production and methane flashing through liquid storage tanks are dominant sources of methane emissions in the Canadian oil and gas sector.  These transient emission sources are challenging to measure, and no comparable field deployable technology currently exists that can accurately measure methane flux in these types of gas streams with variable composition and flowrate.

Results

This project accelerated the development of a novel optical sensor (VentX) capable of continuously and accurately measuring methane emission rates from potential sources at oil and gas production sites, including both casing gas vents and storage tank vents. VentX simultaneously measures both the fraction of methane in a vented gas stream and the velocity of the stream at one- second resolution. These two quantities combine to calculate the true, time-varying methane emission rate of the source.

An initial prototype was successfully developed and tested using laboratory-grade instrumentation and optical components housed in a large enclosure (1 cubic meter).  This prototype was successfully used to measure methane emissions from casing gas vents at heavy oil sites in Saskatchewan, revealing that measured emissions were almost four times greater than reported but consistent with independent aerial measurements.

A refined prototype shrunk these components to a single board, while also making several key improvements to the optical design that further improved measurement accuracy and stability.  The second-generation VentX technology was then successfully deployed in field trials to measure methane emissions from oil storage tanks at upstream production sited in Alberta.  This work provided direct insight into how vent volumes calculated based on gas-oil ratios are prone to underestimation, while also providing new guidance for making direct measurements and for interpretating data from remote measurements.  Project results have been published in peer-reviewed, open-access articles to help ensure maximum uptake by industry and regulators.

Following these field trials, further improvements have been made to the VentX sensor. A new, explosion-proof enclosure has been designed, permitting components to be brought into hazardous environments. The system is now also more compact and can be lifted by a single technician, and has fewer failure points for gas infiltration, a problem observed in the initial field trials.  This new version of the VentX sensor has been deployed internationally, where it was used to measure methane emissions from oil storage tanks as part of UNEP-supported science studies in Colombia.