Well integrity failure resulting in migration of natural gas outside of the surface casing can cause atmospheric greenhouse gas emissions and groundwater quality impacts from existing and historic energy wells. Spatial and temporal variability in gas migration can result in errors in detection (i.e., presence/absence) and efflux estimations. This field-based case study used automated dynamic closed chambers to record repeated (∼every 18 min) CO₂ and CH₄ efflux measurements over a two-week period around a single petroleum production well in Alberta, Canada. Long-term efflux measurements supplemented soil gas compositional and isotopic characterization, along with surface concentration measurements. Effluxes were spatially concentrated around the wellhead and only occasionally detectable more than a few meters away. Estimated total emissions attributable to gas migration ranged from 48 to 466 g CH₄ d⁻¹ (or 0.07–0.7 m³ CH₄ d⁻¹)_. Methane effluxes and concentrations were temporally variable on second-to-hourly and diel scales. Multivariate stepwise regression analysis indicates that multiple meteorological factors, particularly wind speed and air temperature, were related to the temporal variability. Despite temporal variability, elevated concentrations and effluxes were consistently detectable around the well. Major soil gas composition suggests that gas migration near the wellhead causes advective displacement of soil gas, while more distal measurements are indicative of episodic and diffusion-dominated transport. Values of ¹³C–CO₂ and ¹³C–CH₄ samples were consistent with CH₄ oxidation within the unsaturated zone. Although these results reflect a single well, the findings are salient to gas migration detection and emission estimation efforts.

井完整性故障导致天然气从表层套管外部迁移，可能会导致大气温室气体排放以及现有和历史性能源井对地下水质量的影响。气体迁移的时空变化会导致检测错误（即存在/不存在）和流量估计。这项基于现场的案例研究使用自动动态密闭腔室来记录重复的（每18分钟一次）CO ₂和CH ₄在加拿大艾伯塔省的一口石油生产井周围，为期两周的外排量测量。长期外排测量补充了土壤气体的组成和同位素表征以及表面浓度测量。流出物在空间上集中在井口周围，仅在几米外才被发现。估计的可归因于气体迁移的总排放量为48至466 g CH ₄ d ^-1（或0.07–0.7 m ³ CH ₄ d ^-1）_。甲烷外排量和浓度随时间的变化在每小时和迪尔等级上变化。多元逐步回归分析表明，多种气象因素，特别是风速和气温，与时间变化有关。尽管存在时间差异，但在孔周围始终可检测到浓度升高和流出。主要的土壤气体组成表明，天然气在井口附近的迁移会导致土壤气体的对流移动，而更多的远端测量则表明了偶发性和扩散主导性传输。的值¹³ C-CO ₂和¹³ C-CH _4种的样品是一致的，用CH ₄在不饱和区内的氧化。尽管这些结果反映的是单口井，但这些发现对于气体迁移检测和排放估算工作具有重要意义。