Evaluation of Urea-Assisted SAGD Performance Using a 3D Physical Model

Abstract

Steam-assisted gravity drainage (SAGD) is a dominant method for extracting bitumen from oil sands; however, its substantial greenhouse gas (GHG) emissions and water consumption pose significant environmental challenges. To address this, the ES-SAGD process was introduced to curtail these impacts. This study examines the incorporation of urea as an additive in SAGD processes to reduce steam consumption and carbon intensity through three-dimensional physical-model experiments (3DPMEs). This work analyzes essential factors, including the recovery factor, oil production rate, water cut, oil acidity, cumulative gas production and composition, cumulative steam–oil ratio (cSOR), gas–oil ratio (GOR), energy reduction, and carbon tax analysis. The experimental results demonstrate that adding urea to steam as an additive at an optimum urea concentration significantly improves bitumen recovery from 47% OOIP to 74.25% OOIP compared with the baseline SAGD process. Also, the oil production rate increased in most urea-assisted SAGD experiments, except for the 5 wt % case, which dropped below the baseline SAGD experiment, highlighting the need for optimizing the additive concentration. In addition, the average steam–oil ratio (SOR) decreased from 7.6 at 2 PVI for baseline SAGD to about 2.5 at the optimum injected concentration, representing a 67% reduction in SOR and indicating less steam usage and greater energy efficiency. This study demonstrates that although urea decomposes into NH3 and CO2, net CO2 emissions are reduced by 44.61% to 64.50%, indicating a diminished environmental impact on the SAGD process. This reduction is attributed to a substantial decrease in steam injection requirements during the urea-assisted SAGD process, thereby lowering the natural gas (fuel) consumption for steam generation. Crucially, the CO2 emissions avoided by reduced fuel combustion significantly outweigh those generated by urea decomposition during the injection. Urea-assisted SAGD could enhance energy efficiency, minimize greenhouse gas emissions, accelerate the transition to a low-carbon economy, and improve overall sustainability in bitumen recovery.