With legislation around emissions reduction becoming tighter around the world (the US perhaps being the exception), companies are under more pressure to monitor accurately and control emitted gases and potential leaks.
Until recently, that process has been inaccurate and labour intensive, often involving survey work undertaken by human teams equipped with infrared cameras – sometimes by low, slow helicopter missions for remote assets such as pipelines. These teams are deployed several times a year, and at considerable expense given the poor quality of the results.
In January, InnovOil covered Quanta3 and its efforts to test static, sensor-based methane monitoring equipment at Statoil unconventional wells in Texas. However, an altogether new approach has been proposed by Steve Karcher, Phil Lyman and Jarett Bartholomew of Ball Aerospace & Technology.
The team’s solution, Methane Monitor, enables operators to identify methane emissions on the ground from a fixed-wing aircraft. The sensors used are mounted on a single-engine, fixed-wing aircraft – offering lower costs than sensors mounted on helicopters – and can image the full plume of methane gas, allowing real-time detection and quantifying of fugitive emissions.
While many methods use the aforementioned sensor approach, this system is based on LIDAR (Light Detection and Ranging) – or more specifically differential absorption LIDAR, also known as DIAL. As explained by the engineers in their write-up “Embedded DIAL System for Measuring Fugitive Natural Gas Emissions”, this system uses two laser wavelengths: one which is resonates with the molecule of interest, and one which does not. As the on-resonance wavelength is more strongly absorbed by the molecule, the difference between the two signals directly correlates with the amount of the chosen molecule in the laser’s path.
A wavelength of around 1,645.55 nm is used as the on-resonance signal for methane, and is beamed every few nanoseconds, interspersed with a signal which passes straight through the molecule.
Taking anywhere between 1,000 and 10,000 measurements per second, depending on the survey, the DIAL system calculates the difference between the signals to indicate gas concentration. This is collated in an application based on National Instruments’ LabVIEW platform.
These readings are combined with recordings of altitude and geo-location, enabling operators to overlay the plume tracking onto images taken during flight, and/or visualisations such as Google Maps. Doing so also allows users to identify a complete image of the plume from an asset or facility, rather than more widespread or environmental emissions from agriculture, for example.
In the paper, Ball authors note: “We have detected methane flow rates as low as 50 standard cubic feet per hour (SCFH). We can configure Methane Monitor’s sensing swath width up to 200 metres wide. The system has a spatial resolution and geo-location accuracy of better than 2 metres each.” In practice, it means that a small aircraft can collect data over hundreds of miles, all while flying at altitudes of around 1,500 feet, and speeds of 100mph. Pipeline surveys in particular can therefore be done cheaper, faster and more accurately.
Recognising the potential of the system, the innovation recently won the Engineering Impact Award for Energy at National Instruments’ NIWeek 2017.
Ball now intends to incorporate a newer digitiser in its latest generation of Methane Monitor, raising altitude to around 3,000 feet (900 metres) and extending the surveyed area by five times, with a doubling of spatial resolution.
“The next-generation instrument can make cost-effective [surveying] of highly branched, low pressure gas distribution assets possible. It can also facilitate leak [surveys] of oil and gas gathering lines, which are broadly distributed across oil and gas formations,” the team noted.