Cheptonui Fancy, Riddick Stuart N, Hodshire Anna L, Mbua Mercy, Smits Kathleen M, Zimmerle Daniel J
Department of Systems Engineering, Colorado State University, Fort Collins, CO 80523, USA.
Energy Institute, Colorado State University, Fort Collins, CO 80524, USA.
Sensors (Basel). 2023 Oct 12;23(20):8417. doi: 10.3390/s23208417.
Natural gas (NG) leaks from below-ground pipelines pose safety, economic, and environmental hazards. Despite walking surveys using handheld methane (CH) detectors to locate leaks, accurately triaging the severity of a leak remains challenging. It is currently unclear whether CH detectors used in walking surveys could be used to identify large leaks that require an immediate response. To explore this, we used above-ground downwind CH concentration measurements made during controlled emission experiments over a range of environmental conditions. These data were then used as the input to a novel modeling framework, the ESCAPE model, to estimate the below-ground leak rates. Using 10-minute averaged CH mixing/meteorological data and filtering out wind speed < 2 m s/unstable atmospheric data, the ESCAPE model estimates small leaks (0.2 kg CH h) and medium leaks (0.8 kg CH h) with a bias of -85%/+100% and -50%/+64%, respectively. Longer averaging (≥3 h) results in a 55% overestimation for small leaks and a 6% underestimation for medium leaks. These results suggest that as the wind speed increases or the atmosphere becomes more stable, the accuracy and precision of the leak rate calculated by the ESCAPE model decrease. With an uncertainty of ±55%, our results show that CH mixing ratios measured using industry-standard detectors could be used to prioritize leak repairs.
地下管道泄漏的天然气会带来安全、经济和环境危害。尽管通过手持甲烷（CH）探测器进行巡检来定位泄漏点，但准确判断泄漏的严重程度仍具有挑战性。目前尚不清楚巡检中使用的CH探测器是否可用于识别需要立即响应的大型泄漏。为了探究这一点，我们利用了在一系列环境条件下的受控排放实验中进行的地面下风处CH浓度测量。这些数据随后被用作一种新型建模框架——ESCAPE模型的输入，以估算地下泄漏率。使用10分钟平均的CH混合/气象数据并滤除风速<2米/秒/不稳定大气数据，ESCAPE模型分别以-85%/+100%和-50%/+64%的偏差估算小泄漏（0.2千克CH/小时）和中等泄漏（0.8千克CH/小时）。更长时间的平均（≥3小时）会导致小泄漏高估55%，中等泄漏低估6%。这些结果表明，随着风速增加或大气变得更稳定，ESCAPE模型计算的泄漏率的准确性和精度会降低。我们的结果显示，使用行业标准探测器测量的CH混合比的不确定性为±55%，可用于确定泄漏修复的优先级。
