By Paola Leon, Research and Development Advisor for Nakasawa Resources
EOR plays an increasingly important role in the industry, as much of the world’s oil is considered “heavy” or “extra-heavy,” meaning it is inaccessible without these solutions. Because steam quality can (in combination with the correct equipment) greatly improve the rate of oil recovery, lower operating costs, and reduce running time, it is an important – and often overlooked – factor to consider.
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Steam is extremely important to TEOR, with cyclic steam injection being the most common method. In it, saturated steam is injected into the well continuously for a specified period to heat the oil immediately around the well, reducing its viscosity. Once the target viscosity is reached, the steam injection is halted so the heat can spread evenly throughout the reservoir. This allows the oil to be extracted until the well temperature and oil production rate drop and the cycle begins anew.
Quality Steam, Quality Process
Steam quality reflects the ratio of saturated steam (or vapor) in a saturated liquid/vapor mixture. If steam quality is 0%, then the mixture is 100% liquid, meaning it carries much less energy. If it is 100%, then the mixture is entirely vapor – making it much better for energy transfer. In short, steam quality directly impacts how much heat is transmitted, and thus the heat transfer process.
This can have numerous effects, but one of the biggest and most important is on efficiency. All TEOR processes require steam quality to be above 80%, but this still leaves a 20-percentage point gap in quality (and thus efficiency) that can be at least partially closed. For example, steam quality can mean the difference between injecting steam for two months versus six weeks, saving that same two-week period each time the steam injection cycle begins again. This has a massive impact on the reservoir’s profitability, especially over time.
Even high-quality steam requires further assistance to fully realize its benefits. However, if the pipes it travels through are not sufficiently insulated, for example, then steam quality will quickly degrade, even if it began at 100%. It is vital to not only generate high-quality steam but also maintain that quality to its destination with minimal losses.
How to Enhance Steam Quality
The oil & gas industry is always innovating, and this is no less true when it comes to steam quality improvements. New devices are always being developed and introduced to markets to make the oil recovery process faster, less costly, more environmentally friendly, and more efficient.
One way to overcome this challenge is through insulated steam transfer pipes. Traditionally, this was done with insulating materials or liquids, but vacuum-insulated pipes offer better heat preservation. For surface distances of up to 3 kilometers, vacuum-insulated piping can reduce heat losses by up to 13%. One mathematical model found that vacuum insulation methods showed the smallest drop in steam quality from its generator to the well, with losses under 6% per 100m.
But it is crucial to begin with high-quality steam to get the best results. There are solutions available that can deliver steam with a quality of 95% or higher, but even these are best when combined with careful insulation. When a high-quality steam generator produces steam close to 100% pure and injects it to the well through vacuum-insulated tubing, the operational results can be excellent.
Some generation equipment, when paired with vacuum-insulation, can achieve an extra 12% injected heat, leading to an oil production increase of 15% or more, a 12% reduction in feedwater usage, significant steam-to-oil ratio (SOR) improvements, and a 25% decrease in operational costs on large-scale steam injection projects overall.
All of these improvements can be realized through an increase in steam quality because it directly correlates to the amount of energy transferred during the process. With the rising need to extract heavy and extra-heavy oil, relying on 80% quality steam becomes an increasing challenge to both operational costs and timelines.
Given the growing need for heavy oil extraction and the important role of TEOR, it is well past time for the industry to raise its steam quality standards. It is only by starting with high-quality steam that companies can achieve the kind of cost-effective and highly efficient results they need to stay competitive in today’s world.