Bitumen extraction for the production of synthetic crude oil in Canada's Athabasca Oil Sands industry has recently come under spotlight for being a significant source of greenhouse gas emission. A major cause of concern is methane, a greenhouse gas produced by the anaerobic biodegradation of hydrocarbons in oil sands residues, or tailings, stored in settle basins commonly known as oil sands tailing ponds. In order to determine the methane emitting potential of these tailing ponds and have future methane projections, we use real-time weather data, mechanistic models developed from laboratory controlled experiments, and industrial reports to train a physics constrained machine learning model. Our trained model can successfully identify the directions of active ponds and estimate their emission levels, which are generally hard to obtain due to data sampling restrictions. We found that each active oil sands tailing pond could emit between 950 to 1500 tonnes of methane per year, whose environmental impact is equivalent to carbon dioxide emissions from at least 6000 gasoline powered vehicles. Although abandoned ponds are often presumed to have insignificant emissions, our findings indicate that these ponds could become active over time and potentially emit up to 1000 tonnes of methane each year. Taking an average over all datasets that was used in model training, we estimate that emissions around major oil sands regions would need to be reduced by approximately 12% over a year, to reduce the average methane concentrations to 2005 levels.
翻译:加拿大阿萨巴斯卡油砂工业中用于生产合成原油的沥青提取工艺,近期因成为温室气体排放的重要来源而备受关注。主要担忧源于甲烷——一种由油砂残渣(即尾矿)中碳氢化合物在厌氧生物降解过程中产生的温室气体,这些尾矿储存于通常称为油砂尾矿池的沉降池中。为评估这些尾矿池的甲烷排放潜力并进行未来甲烷预测,我们利用实时气象数据、基于实验室控制实验开发的机理模型及工业报告,训练了一个物理约束的机器学习模型。我们训练的模型能成功识别活跃尾矿池的方位并估算其排放水平,这些数据通常因采样限制而难以获取。研究发现,每个活跃的油砂尾矿池每年可能排放950至1500吨甲烷,其环境影响相当于至少6000辆汽油动力车辆的二氧化碳排放量。尽管废弃尾矿池常被认为排放量可忽略,但我们的发现表明这些尾矿池可能随时间推移转为活跃状态,每年潜在排放量可达1000吨甲烷。通过对模型训练所用全部数据集取平均值,我们估算主要油砂区域周边排放量需在一年内降低约12%,方能使平均甲烷浓度降至2005年水平。