Publications & Presentations

Quantitative Gas Imager and Leak Rate Estimator

Nicholas F. Aubut, Richard T. Wainner, Shin-Juh Chen, and Michael B. Frish
FLAIR 2018 - Field Laser Applications in Industry and Research, September 10-14, 2018, S. Maria degli Angeli (Assisi), Italy

Natural gas pipeline leakage poses safety hazards, contributes to greenhouse gas loads, and costs customers the price of lost gas.

The principal purpose of developing rapid and remote leak rate measurement techniques is to rank leaks based not only on the current practice of measuring local concentration (which can be very high for a small leak in a no wind condition), but also on measuring leak rate. No current leak survey tool directly images gas leak plumes quantitatively, much less quantifies emission rate, a technology gap that this sensor development addresses. The technology under development, which we call “RMLD-QGI” (Quantitative Gas Imager), combines low-cost laser scanner, visible camera, and near-IR tunable diode laser absorption spectroscopy (TDLAS) gas detection to answer this need.

Natural Gas Fugitive Leak Detection Using an Unmanned Aerial Vehicle: Localization and Quantification of Emission Rate

Levi M. Golston, Nicholas F. Aubut, Michael B. Frish, Shuting Yang, RobertW. Talbot, Christopher Gretencord, James McSpiritt, and Mark A. Zondlo
Atmosphere 2018, 9(9), 333

We describe a set of methods for locating and quantifying natural gas leaks using a small unmanned aerial system equipped with a path-integrated methane sensor. The algorithms are developed as part of a system to enable the continuous monitoring of methane, supported by a series of over 200 methane release trials covering 51 release location and flow rate combinations.

The system was found throughout the trials to reliably distinguish between cases with and without a methane release down to 2 standard cubic feet per hour (0.011 g/s). Among several methods evaluated for horizontal localization, the location corresponding to the maximum path-integrated methane reading performed best with a mean absolute error of 1.2 m if the results from several flights are spatially averaged. Additionally, a method of rotating the data around the estimated leak location according to the wind is developed, with the leak magnitude calculated from the average crosswind integrated flux in the region near the source location. The system is initially applied at the well pad scale (100–1000 m2 area). Validation of these methods is presented including tests with unknown leak locations. Sources of error, including GPS uncertainty, meteorological variables, data averaging, and flight pattern coverage, are discussed. The techniques described here are important for surveys of small facilities where the scales for dispersion-based approaches are not readily applicable.

Natural Gas Fugitive Leak Detection Using an Unmanned Aerial Vehicle: Measurement System Description and Mass Balance Approach

Shuting Yang, RobertW. Talbot, Michael B. Frish, Levi M. Golston, Nicholas F. Aubut, Mark A. Zondlo, Christopher Gretencord, and James McSpiritt
Atmosphere 2018, 9(10), 383

Natural gas is an abundant resource across the United States, of which methane (CH4) is the main component. About 2% of extracted CH4 is lost through leaks. The Remote Methane Leak Detector (RMLD)-Unmanned Aerial Vehicle (UAV) system was developed to investigate natural gas fugitive leaks in this study.

The system is composed of three major technologies: miniaturized RMLD (mini-RMLD) based on Backscatter Tunable Diode Laser Absorption Spectroscopy (TDLAS), an autonomous quadrotor UAV and simplified quantification and localization algorithms. With a miniaturized, downward-facing RMLD on a small UAV, the system measures the column-integrated CH4 mixing ratio and can semi-autonomously monitor CH4 leakage from sites associated with natural gas production, providing an advanced capability in detecting leaks at hard-to-access sites compared to traditional manual methods. Automated leak characterization algorithms combined with a wireless data link implement real-time leak quantification and reporting. This study placed particular emphasis on the RMLD-UAV system description and the quantification algorithm development based on a mass balance approach. Early data were gathered to test the prototype system and to evaluate the algorithm performance. The quantification algorithm derived in this study tended to underestimate the gas leak rates and yielded unreliable estimations in detecting leaks under 7 x 10-66 m3/s (~1 Standard Cubic Feet per Hour (SCFH)). Zero-leak cases can be ascertained via a skewness indicator, which is unique and promising. The influence of the systematic error was investigated by introducing simulated noises, of which Global Positioning System (GPS) noise presented the greatest impact on leak rate errors. The correlation between estimated leak rates and wind conditions were investigated, and steady winds with higher wind speeds were preferred to get better leak rate estimations, which was accurate to approximately 50% during several field trials. High precision coordinate information from the GPS, accurate wind measurements and preferred wind conditions, appropriate flight strategy and the relative steady survey height of the system are the crucial factors to optimize the leak rate estimations.

Monitoring fugitive methane emissions utilizing advanced small unmanned aerial sensor technology

Nicholas F. Aubut, Matthew C. Laderer, Shuting Yang, Robert W. Talbot, Levi M. Golston, Mark A. Zondlo, Paul D. Wehnert, and James Rutherford
27th World Gas Conference, June 25-29, 2018, Washington, DC

We integrated backscatter laser technology with a small Unmanned Aerial Vehicle to create a new platform for natural gas leak survey and quantification. Simulated flights with the sensor system

deployed on a rotating 10m diameter boom successfully located and quantified emission rates from a known methane source. Actual low-altitude flights conducting raster pattern surveys of wellhead
infrastructure located, visualized, and estimated flux from leaks smaller than 5 scfh.

Scanning, standoff laser-based leak imaging and quantification

Nicholas F. Aubut, Richard T. Wainner, Matthew C. Laderer, Paul D. Wehnert, and James Rutherford
27th World Gas Conference, June 25-29, 2018, Washington, DC

This paper reports a novel quantitative methane plume imaging tool, based on active near-infrared backscatter laser sensing technology. It integrates a laser sensor with a video camera in a future handheld

package to create a highly sensitive imager that also quantifies emission rate. It provides colorized quantified images of path-integrated methane concentration independent of background. The images depict methane plumes overlaid on a visible camera image of the background. This new tool addresses the need for reliable, robust, low-cost sensors to detect, image, and quantify fugitive methane emissions, enabling operators to prioritize repairs. We built a prototype platform that demonstrated quantitative performance in the laboratory and municipal field tests. Based on measured signal-to-noise ratios, it can quantify emissions as small as 0.25 scfh in seconds.