Advanced Techniques for Autonomous Detection of Gas Releases
Authors: Abdel-Moati H. M. , Morris J. M. , Ruan Y.. , Zeng Y.. 
Published: September 2014

Hydrocarbon leaks in large scale LNG and gas processing and handling facilities present a risk to health and safety, as well as a negative impact on the environment. Existing autonomous leak detection systems rely primarily on point and path detection. This technology requires dispersed gas to physically contact the point sensors or move between two path detectors. Manual leak checks are also performed periodically by checking one component at a time using a flame ionization detector (FID) or optical gas imager, however the size and complexity of these facilities means that smaller leaks may go undetected for extended periods of time and unintended releases may occur when plant personnel are not present. 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 gas imaging technology to autonomously scan for and identify leaks.

The IntelliRed™ system utilizes a unique mid-wave IR (MWIR) imager and a computer vision algorithm that analyzes the video output from the IR imager to determine the presence of hydrocarbon plumes. Most hydrocarbons have strong absorbance peaks in a narrow MWIR region. The algorithm takes advantage of the difference in contrast between a hydrocarbon plume and the background in an IR imager. The algorithm compares sequentially collected IR images and uses a multi-stage confirmation process to model the behavior of the plume and confirm the detection. It has multiple filters that mitigate interferences such as humans, vehicles, and trees. After extended pilot deployments, the IntelliRed™ technology has been qualified and is commercially available for leak detection and environmental applications.

An innovative differential infrared (DIR) camera design now offers the possibility of lower detection limits and higher immunity to false alarms for the IntelliRed™ system. The design employs two cooled MWIR sensors with a common optical path. The infrared energy from the scene is divided using a beam splitter, focusing a spatially registered image on each sensor. The spectral filtering for the two sensors is chosen so that one sensor can visualize a hydrocarbon plume while the second sensor cannot. A synchronized system clock for the two sensors ensures that the frames are temporally aligned. The result is a camera which produces both spatially and temporally aligned frames with the plume present in one frame but absent in the other. A differential image is produced by comparing the two sensors frame by frame, providing a robust filter for common interferences such as steam and dust plumes.

The DIR camera design requires new computer vision techniques to exploit the information provided by the reference sensor. Results are compared to other autonomous hydrocarbon detection technologies, including single sensor IntelliRed™ technology. New applications enabled by the DIR camera design are discussed, including aerial pipeline surveys. The technology is currently being qualified with DIR based IntelliRed™ pilot deployments underway in Qatar and the United States.