Autonomous Remote Gas Detection Using Optical Imaging Technology

Identifying fugitive emissions from large scale LNG and gas processing and handling facilities is a difficult time and resource intensive process. Because of the limitations of hand held gas detection devices, and the sheer size and complexity of these facilities, smaller leaks may go undetected for extended periods of time and unintended releases may occur when plant personnel are not present or the area monitored.  Reducing the total emissions from a large plant or a regional industry footprint could very well have an appreciable positive impact on the environment.  Further, early detection of hydrocarbon leaks using a continuous monitoring system can reduce the risk of potentially serious safety incidents that can result from ignition of gas plumes.

ExxonMobil Research Qatar Ltd. and Providence Photonics LLC have developed the IntelliRed™ Remote Gas Detection system that integrates computer vision algorithms and infrared (IR) optical technology that can autonomously scan for and identify small leaks such as those associated with fugitive emissions. Efficient identification of these emission sources will lead to better control and maintenance activities.

A single sensor version of the IntelliRed™ system utilizes a custom build component based IR camera and integrated cooler assembly, and a computer vision algorithm that analyses the video output from the IR imagers to determine the presence of hydrocarbon plumes. Most hydrocarbon plumes have strong absorption peaks in the narrow mid-wave IR region. The algorithm takes advantage of the difference in contrast between a hydrocarbon plume and the background in each pixel of an IR image and the temporal changes due to plume behavior for the analysis. The algorithm compares sequentially collected IR images and uses a multi-stage confirmation process to confirm the detection and has built-in multiple filters that mitigate interferences like steam, and other moving objects such as humans and trees. Early field tests indicate that a 4 lb/hr propane leak could be autonomously detected from a distance of up to 800 feet. Also, rigorous field tests comparing the IntelliRed™ system to point and path detectors showed that the system was successful in detecting leaks from 300 feet that barely elicited a response from a point and path detector array that was located only 5 feet from the leak source.

A dual sensor version of the IntelliRed™ system utilizes two cooled mid-wavelength IR (MWIR) sensors with a common optical path resulting in a differential infrared (DIR) camera. The infrared energy from the scene is split between two sensors and the spectral band pass filtering for the two sensors is chosen so that one sensor can see the hydrocarbon plume while the second sensor cannot.  The two sensors are synchronized spatially and temporally to ensure that successive frames are aligned correctly. Image subtraction techniques are used to produce a differential image that eliminates the background, thus filtering out interferences such as dust and steam and allowing for leak detection while the system is in motion without the need for image stabilization.

The IntelliRed™ system is currently deployed for a long term pilot at two process facilities, one in the US and one in Qatar, with more deployments being planned. Results from field testing at these process facilities will help researchers investigate the effect of temperate and harsh weather conditions, the effect of varying temperatures and gain a better understanding of equipment wear and tear, maintenance requirements and possible life expectancies. These data sets will produce an accurate assessment of the performance of the system under actual working conditions.