An Overview of the New Breed of Methane Sensor Technologies

If you're looking for professional advice on methane analysis by means of an open-path laser-absorption spectrometer or a mid-infrared tunable-diode laser spectroscope, follow the links for the relevant e-Learnings. Similarly, if you're in need of information on hyperspectral infra-red imaging for any-state methane, take a look at Jean-Phillipe Gagnon of Telops Inc.'s lecture on the topic.

In 2014 the US Department of Energy's ARPA-E program initiated MONITOR, a 45M US$ investment in methane detection technologies. The eleven technologies funded under the program are reaching the end of their second development year and beginning field testing. Initial testing has been performed at the Methane Emissions Test and Evaluation Center (METEC) at Colorado State University, which reproduces emissions behavior at oil & gas (O&G) wells, small compressor stations, and underground gas gathering lines. In addition to MONITOR, many other sensor advanced technologies are under development. This presentation will provide an overview of the technologies, discuss new deployment methodologies required for these technologies, and the methods required to test both.

Sensor technologies: Applying the recent breakthroughs in lasers, fabrication and computation, companies have been able to reduce the cost of cavity ring down and mass spectrometer instruments by an order of magnitude with only minor decreases in sensitivity. Applying similar technologies, bulky infrared cameras have been reduced in size and cost by a similar magnitude. Utilizing a variety of sensing methods, new stationary sensors have low per-unit costs, opening the possibility of continuous deployment and monitoring.

Deployment methodologies: Deployment these new sensor technologies requires more than breakthroughs in the cost and performance of the sensors. The sensors require several innovative deployment methodologies unlike previous sensing strategies. Point sensors rely on variation in wind speed and direction over extended periods to back-propagate methane concentration to source location and emission rate. These arrays of low-cost sensors provide continuous monitoring, but also require continuous data collection and atmospheric modeling to effectively isolate emission sources. Camera or laser sensors may be effectively deployed on unmanned aerial vehicles (drones or UAVs) which "box" facilities, determine if abnormal emissions are occurring, and then trace emissions to the source. Finally, long-path laser technologies provide a capability to screen large areas for emissions. Current projections indicate circular fields-of-view 1-5 kilometers in radius. As with point sensors, these technologies rely on wind speed and direction to trace path-integrated concentration measurements to source locations.

Testing methods: New monitoring methods require a different take on assessment methods. Previous methods relied on near-field measurement of emissions (e.g. EPA Method 21) or close-in observation of emission sources (e.g. optical gas imaging), performed by trained human operators. New sensor technologies frequently utilize wind fields and extended measurement periods coupled with high-speed wind measurements and complex atmospheric models. While a "methane bottle in a parking lot" can be utilized for initial testing, efficacy can only be assessed when conditions replicate the wind fields, concentration, and diffuse emission points seen on O&G facilities. These methods require testing in topographically realistic conditions (i.e. real facility equipment in proper position), for extended periods (weeks), with precisely controlled releases (multiple points, multiple rates). In addition, many O&G facilities have both planned, intermittent, emissions - pneumatic controllers, liquid unloadings, blowdowns - and abnormal emissions, such as leaks or device failures. Testing conditions must present a realistic mix of these sources, challenging technologies to separate planned emissions from leak sources