Non-Condensable Gas Distribution in SAGD Chamber
- Jian-yang Yuan (Osum Oil Sands Corp) | Joyce X. Chen (Alberta Innovates - Technology Futures) | Gerry Pierce (Alberta Innovates - Technology Futures) | Brian Wiwchar (Alberta Innovates - Technology Futures) | Hart Golbeck (Alberta Innovates - Technology Futures) | Xinkui Wang (Alberta Innovates - Technology Futures) | Gilles Beaulieu (Alberta Innovates - Technology Futures) | Shauna Cameron (Alberta Innovates - Technology Futures)
- Document ID
- Society of Petroleum Engineers
- Canadian Unconventional Resources and International Petroleum Conference, 19-21 October, Calgary, Alberta, Canada
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 2 Well Completion, 5.1.1 Exploration, Development, Structural Geology, 4.1.2 Separation and Treating, 4.1.5 Processing Equipment, 2.4.3 Sand/Solids Control, 5.4.6 Thermal Methods, 4.2 Pipelines, Flowlines and Risers, 5.4.2 Gas Injection Methods, 4.6 Natural Gas, 5.1.9 Four-Dimensional and Four-Component Seismic, 5.2.1 Phase Behavior and PVT Measurements, 5.8.5 Oil Sand, Oil Shale, Bitumen, 5.3.9 Steam Assisted Gravity Drainage, 4.3.4 Scale, 5.5.8 History Matching, 5.5.2 Core Analysis
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This paper summarizes a set of SAGD experiments conducted live under an X-ray scanner. These experiments were specifically designed for mapping non-condensable gas distribution and their movement in an active steam chamber during SAGD.
Many researches over the past three decades have shown that non-condensable gases may have critical impacts on SAGD performance. Some may be positive; others may be negative depending on reservoir and operating conditions. For better utilizing the positives, avoiding the negatives and for better SAGD performance predictions, it is crucial to understand how these gases behave in a steam chamber. It is arguable that non-condensable gases tend to accumulate at the steam front where steam condenses. However, this assertion has only been supported by numerical simulations. Field observation data have been too sparse. Meaningful tracking of gas production is not a normal practice in the field.
The first experiment was conducted in an aluminum vessel packed with 4Darcy sands at 1.0MPa. The second experiment was conducted in a scalable system consisting of a titanium pressure vessel and a PEEK cell, allowing the SAGD experiment ran at 2.1MPa. Both experiments used bitumen fully saturated with methane at reservoir conditions and were run live under the X-ray scanner. X-ray images were taken at given time intervals. Temperature profiles were obtained directly from thermocouples. Density profiles were computed from the X-ray images. Methane in free gas phase were calculated and mapped. After each experiment, samples from opened cell were also tested for additional observation and confirmation.
These experiments confirmed the assertion that non-condensable gas tends concentrate along the steam front. It also demonstrated that the steam temperature zone does not coincide with the oil depleted zone, indicating that in a SAGD reservoir with nontrivial presence of non-condensable gases, temperature measurements at observation wells alone would not reflect the boundary of the steam chamber. The more representative measure of a steam chamber should be the mapping of oil depleted zone. 4D seismic plus a more comprehensive monitoring of gas production would be needed for determination of the oil depleted zone in the field operation.
In a live oil reservoir, a SAGD operation can generate significant amount of free non-condensable solution gas, mainly methane. How does it impact SAGD performance? This has been a question asked for many times [1-27] since 1980's. Numerical simulations consistently indicate that non-condensable gases would tend to accumulate at the steam front. This accumulation of non-condensable gas would reduce the temperature gradient perpendicular to the steam front. Therefore, it would slow down the heat transfer into the cold oil zone, impeding steam chamber expansion and reducing oil production [10, 17, 19-21, 24-27]. On the other hand, this gas accumulation would reduce the contact area to the overburden and form a gas rich layer acting as an insulator, reducing heat loss into the overburden. Therefore, non-condensable gases, either from solution gas or injected gas, would help improving steam to oil ratio [7-25]. Studies on limitedly available field data have not reached definitive conclusions [1-6, 18] that would either support or against the numerical simulation results. This makes laboratory scale study a necessity.
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