Using controlled subsurface releases to investigate the effect of leak variation on above-ground natural gas detection

Pipelines transport natural gas (NG) in all stages between production and the end user. The NG composition, pipeline depth, and pressure vary significantly between extraction and consumption. As methane (CH4­), the primary component of NG is both explosive and a potent greenhouse gas, NG leaks from underground pipelines pose both a safety and environmental threat. Leaks are typically found when an observer detects a CH4 enhancement as they pass through the downwind above-ground NG plume. The likelihood of detecting a plume depends, in part, on the size of the plume, which is contingent on both environmental conditions and intrinsic characteristics of the leak. To investigate the effects of leak characteristics, this study uses controlled NG release experiments to observe how the above-ground plume width changes with changes in the gas composition of the NG, leak rate, and depth of the subsurface emission. Results show that plume width generally decreases when heavier hydrocarbons are pr..., The dataset is processed data for experiments that were conducted at conducted on the ‘rural testbed’ at Colorado State University’s Methane Emissions Technology Evaluation Center (METEC) in Fort Collins, CO, US, between April and June 2022. Four inlets were fixed at 0.5, 2, 5, and 7 m AGL on an 8 m stainless-steel mast 7 m northwest of the subsurface emission point. The four inlets were connected to the ABB LGR multiplexor  via 30 m lengths of PTFE tubing (1/8\" ID x 1/4\" OD x 1/16\" Wall Tygon® 2375 Ultra Chemical Resistant Tubing) which sampled each height for one minute sequentially. The outlet of the multiplexer was connected to a VACUUBRAND GMBH + CO KG MD1 vacuum pump and then tee-ed to an ABB LGR-ICOS GLA 132 Ultraportable Greenhouse Gas Analyzer (UGGA). The UGGA is a laser absorption spectrometer measuring methane, carbon dioxide, and water mole fractions in an air sample. It reports mole fractions each second, with a stated precision of 1.4 ppb at 1 Hz, 0 to 100 ppm linear measu..., , # Using controlled subsurface releases to investigate the effect of leak variation on above-ground natural gas detection

The dataset is a combination of methane measurements from the Ultraportable Greenhouse Gas Analyzer and meteorological data from the ultrasonic anemometer. This dataset is processed from the raw data in the following order:

1. The meteorological data was converted from the epoch time to the George date; the original sonic data was split into separate dates.
2. The 3D wind vectors u, v, and w were calculated from wind direction, wind speed, and wind elevation.
3. The UGGA raw data were unzipped, converted to TXT files, then to CSV files.
4. From the processed UGGA data, the following were extracted: Time,[CH4]\_ppm, MIU valve, and MIU desc variables.
5. For each experiment, multiple files were combined into daily files.
6. The Monin-Obukhov length was calculated every 15 minutes and converted to Pasquill-Gifford classification.

Files

* Experiment\_1.UGGA.MET.2022-0...