The majority of oil sands production uses Steam Assisted Gravity Drainage (SAGD), a process that warms the bitumen in an oil sands reservoir by injecting steam, which allows the heavy product to flow and be moved to the surface. The water returned to the surface with the bitumen is treated at a Central Processing Facility (CPF) to be re-used by turning it into usable steam for injection back into the reservoir. Due to the high temperature of the water, it must be cooled before it can be treated and recycled, which relies on heat exchangers. The process of heating and then cooling the water leaves a buildup of minerals, which reduces the equipment’s effectiveness. Due to fouling, caused by the buildup and scaling on the interior of the equipment, the exchangers require frequent maintenance, increasing water usage, cleaning chemicals, greenhouse gas emissions, downtime and costs.
In 2014, COSIA’s Water Environment Priority Area (EPA) issued a Challenge to find fouling-resistant heat exchangers. COSIA’s Challenges are articulations of the innovation requirements for a specific issue. COSIA’s Challenge statements help mobilize innovators from across the globe, in oil and gas and other industries, to present possible solutions for addressing member companies’ needs. In the Fouling Resistant Heat Exchangers Challenge, COSIA was looking for a way to make heat exchangers that did not accumulate scaling and buildup in its internal tubing.
While the Challenge went out to the world, the Water EPA member companies continued their own exploration for solutions to address the fouling of existing heat exchangers. They discovered that trying to find a novel design to make heat exchangers completely impervious to fouling was not a practical pursuit, in part because of the cost required to do so and also because numerous other efforts looking to refine the process for heating and cooling produced water for steam injection and re-use being used by in situ operations.
However, through their combined knowledge and collaborative sharing of operational best practices and new technologies, solutions surfaced within their own network. The Water EPA identified multiple solutions to help manage the fouling issue, reducing water usage, cleaning chemicals, greenhouse gas emissions, downtime and costs.
Members of COSIA’s Water EPA with in situ facilities have addressed the issue of heat exchanger fouling in a variety of ways. The In Situ Water Best Practices Working Group has brought company experts together to share best practices and improve technologies that advance operational and environmental performance improvements. The Working Group has shared information to monitor the extent of the fouling, use chemicals online to clean and protect the equipment, and modify operating conditions to mitigate fouling.
Other solutions that have been shared at COSIA include:
- Online cleaning mechanisms: the use of internal cleaning mechanisms means that the heat exchangers can be maintained while they are operational, without an equipment shutdown. One type, the “brush and basket,” uses brushes to sweep inside the tube of the exchanger, pushing the build-up into containers at the end, which can be removed and cleaned. Another technology uses sponge balls for a similar purpose to clear the scaling from inside the unit.
- Fouling-resistant Coating: while heat exchangers require up to weekly maintenance cleaning, coating the interior of the tubes could extend the maintenance to a period of years.
The Water EPA has introduced best practices, procedures and technologies that have improved water usage and reduced greenhouse gas emissions of heat exchangers.
The issue of fouling of heat exchangers is one that companies operating in situ facilities in the Water EPA recognized and addressed together. Members of the In Situ Water Best Practices Working Group, made up of BP, Canadian Natural, Cenovus, ConocoPhillips Canada, Devon, Imperial Oil, Nexen, Shell Canada, Statoil and Suncor Energy, successfully shared best practices, procedures and technologies to improve the issue of fouling in heat exchangers.
“While the fouling of heat exchangers remains an issue for the oil sands industry, we have recognized improvements,” says Dave Rowley, ConocoPhillips Canada’s water technology lead and lead for COSIA’s In Situ Water Best Practices Working Group. “We will continue to examine ways to do things like extend the time between cleanings and share these learnings with each other. We are excited to put the call out to innovators and potential collaborators from around the globe to address other Water Challenges, in particular one for high temperature de-oiling and water treatment technologies, such as membranes, which may eliminate the need for this type of heat exchanger all together.”