Non-Condensable Gas Co-Injection to Maintain Reservoir Pressure and Reduce Emissions
ConocoPhillips Canada developed a low-cost technology that leverages existing in-situ infrastructure at steam assisted gravity drainage (SAGD) facilities to address energy-intensive thief zone interactions. Funded through ERA #2: Oil Sands Innovation in 2017, this pilot successfully demonstrated that non-condensable gas (NCG) co-injected with steam minimizes thermal losses to the thief zone and helps maintain reservoir pressure, resulting in reduced steam oil ratio and greenhouse gas (GHG) emissions.
“Thief zones” is a term used in oil and gas operations that refers to zones of water in the formation over top the oil and gas zones of interest that can cause efficiency losses in SAGD operations. They’re formed when those water zones come into hydraulic communication with the steam used in SAGD. Interactions with thief zones reduce reservoir pressure, requiring increased steam injection to maintain suitable pressures for oil production. This leads to higher steam to SORs and GHG emissions from natural gas combustion for steam generation.
ConocoPhillips mitigated this problem by co-injecting NCG alongside the steam used in SAGD. The NCG can replace the ‘sacrificial’ steam otherwise lost to the thief zone, which in turn displaces the top water, reducing heat and pressure losses. Additionally, because the technology leverages existing in-situ infrastructure at SAGD facilities, it can be implemented without the need for significant additional investments or changes to the current operations.
Use of Innovative Modelling to Accelerate Field Operations
ConocoPhillips validated the use of gas co-injection via extensive reservoir simulation work, then piloted its use at a well pad at the Surmont SAGD project. The NCG pilot field was completed in 2019 and successfully demonstrated a 30 to 35 per cent SOR reduction compared to the dynamic baselines and saved five million barrels of steam. The project highlighted the importance of accurate reservoir modeling, including the use of flexible grid modelling (FGM) and virtual wells to simulate extensive thief zones.
FGM is an updated method of geologic modelling that recently became an alternative to the standard hybrid modelling method. FGM has unique functionality that allows the modelling to be more adjustable and responsive to the project’s needs. Utilizing these techniques helped validate the NCG mechanisms and pilot performance without significant cost. This increased the confidence level for the technology and supported the case for commercialization of the technology and execution of the pilot. These techniques were crucial for understanding the reservoir’s response to NCG co-injection and provided insights for field strategy and planning, leading to the pilot’s successful implantation.
What’s next?
Since this project’s completion, NCG co-injection technology has progressed from pilot projects to broader commercial deployment. The technology first expanded into adjacent pads. As years passed, it has been successfully implemented at many SAGD sites, continuing to demonstrate reductions in greenhouse gas emissions and operating costs. As of 2020, ConocoPhillips has over 60 well pairs on CNG co-injection and plan to apply this technology to more sites moving forward.