Subcool, Fluid Productivity, and Liquid Level Above a SAGD Producer
- Jian-Yang Yuan (Osum Oil Sands Corporation) | Daniel Nugent (Osum Oil Sands Corporation)
- Document ID
- Society of Petroleum Engineers
- Journal of Canadian Petroleum Technology
- Publication Date
- September 2013
- Document Type
- Journal Paper
- 360 - 367
- 2013. Society of Petroleum Engineers
- 5.3.9 Steam Assisted Gravity Drainage, 5.1.1 Exploration, Development, Structural Geology
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- 622 since 2007
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Thermodynamic steam-trap control, or subcool control, in a typicalsteam-assisted gravity-drainage (SAGD) production is essential to the stabilityand longevity of the operation. It is achieved commonly through the control offluid production. The goal of such control is to maintain a steady and healthyliquid production without allowing steam from the injector to bypass to theproducer. Therefore, it is effectively a control of the liquid level above theproducer. Unfortunately, it is not practical to monitor this liquid level. Arule-of-thumb subcool-per-metre estimation of 10°C/m of liquid level is popularin the industry; however it does not prove to hold in many situations. Thispaper presents a study of the dynamics of SAGD-production control with aresulting algebraic equation that relates subcool, fluid productivity, andwellbore drawdown to the liquid level above a producer. The main conclusions ofthis study include
- There is no minimum subcool value for a pure-gravity-drainage scenario;however, as the wellbore drawdown is considered, there is a minimum subcoolvalue in order to maintain the stability of fluid flow.
- For a given productivity, the liquid level increases as subcool increasesor as wellbore drawdown decreases.
- For each given set of operating parameters, there exists a criticalproductivity below which SAGD operation would halt.
- Before the steam chamber reaches the top of the reservoir, the fluidproductivity is limited by the vertical distance between the injector and theproducer; the larger the distance, the higher the fluid production rate canbe.
A verification of this analysis was conducted by a series of numericalreservoir simulations. Although limited to two dimensions, we expect that thisanalysis captures the main physics amid the dynamic complexity ofSAGD-production control. The resulting algebraic equation can be used forbetter understanding of the dynamics of subcool control and for determiningoperation strategies.
|File Size||1 MB||Number of Pages||8|
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