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Estimating water saturation in a water zone above steam-heated bitumen.
A Steam-Assisted Gravity Drainage project is proposing to use water from a water zone over a bitumen reservoir, for steam injection into the base of the bitumen pay zone. Thermal simulations indicate the water zone will be heated to 230C by heat rising through the bitumen, and available drawdown will be depleted to near the top of the water zone.
The question is regarding the sustainability of this process, as there is potential risk of steam exclusion breaking off water production from the water zone.
The proponent has used FEFLOW to model heat migration, but there is no modeling of water saturation. Would iTOUGH2 be appropriate for estimating water saturation as a result of water withdrawals and heat inputs?
1 reply
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Hi Robert,
Seems like a challenging, interesting problem (I'll contact you by e-mail to get some clarification).
Since you submitted this question to the iTOUGH2 Forum, I take the opportunity to clarify what iTOUGH2 does as opposed to (or in addition to) TOUGH2. iTOUGH2 does Parameter Estimation (among other things), i.e., it estimates (INPUT) parameters by automatically calibrating the model against observable (OUTPUT) variables. When you ask about "estimating water saturation", I presume you use the term "estimating" in the sens of "calculating" or "predicting". Water saturation is usually an OUTPUT variable, i.e., the solution variable of the forward model - it can thus be "estimated" using standard TOUGH2, i.e., you would not need iTOUGH2. Note that iTOUGH2 can be used for standard forward modeling as well. Moreover, water saturation can indeed be a parameter to be estimated in the inverse sense; however, what you are estimating then is water saturation as an initial condition, as it has to be an INPUT parameter to the forward model, not an OUTPUT variable. Also note that you could use iTOUGH2 for sensitivity and uncertainty analyses, e.g., to evaluate how the water saturation changes as a result of uncertainty in water withdrawal rates, heat inputs, and hydrogeological and thermal properties. Hope these few remarks are useful.
Stefan