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T.C. Onstott

missing H2O

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Greetings,

I've been running a combined flush with reaction program and have come across a perplexing problem. I noticed my porosity plummeting and crashing the simulation. At first I thought it must be due to mineral precipitation, but as I examined the output more closely I noticed that my solvent mass was decreasing, even though I was flushing, which I've assumed meant I was constant replenishing solvent mass. I couldn't identify any mineral dissolution or formation reaction that could account for the solvent mass loss. So I'm flummoxed.

I'm using React 7.04, PC platform. see attached code and output.

React_output.txt

newGullfaksSRB100.txt

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Greetings,

I've been running a combined flush with reaction program and have come across a perplexing problem. I noticed my porosity plummeting and crashing the simulation. At first I thought it must be due to mineral precipitation, but as I examined the output more closely I noticed that my solvent mass was decreasing, even though I was flushing, which I've assumed meant I was constant replenishing solvent mass. I couldn't identify any mineral dissolution or formation reaction that could account for the solvent mass loss. So I'm flummoxed.

I'm using React 7.04, PC platform. see attached code and output.

Hi T.C.

I see two issues.

First, the mass of solvent loss per reaction path increment is small - by my calculations, .01 g H2O. I'll speculate as to why this might be occurring below. The bigger issue is again the number of reaction path steps forced by the Flush configuration. You are adding ~24,000 kg of meteoric H2O (plus dissolved components) to a pore volume that initially contains .167 kg of saline H2O (plus dissolved components). In the Flush configuration React can only remove and displace the amount of fluid present in the Basis, and this amount decreases during your reaction path model. This means your reaction path model initially requires a minimum of ~150,000 steps - the step size decreases as the mass of solvent in your Basis decreases. The gradual decrease in solvent mass keeps the model from progressing to completion, even though you have a significant remainder of meteoric fluid to flush through your reservoir.

I'm not sure as to the actual reason for the solvent mass decrease. One reason may be that you've defined Monohydrocalcite as the stable source of bicarbonate in your reservoir - the database actually favors Calcite, and during speciation will replace the Monohydrocalcite with Calcite, which affects your solvent mass. A second reason may have to do with how React removes and replaces fluid during each step of the Flush configuration - I'm not sure if it is a mass per mass replacement, and whether the replacement is based on the mass or volume of solvent or solution flushed from the system. Since your Basis and Reactants concentrations are somewhat different, this could also affect the remaining mass of solvent after every reaction path increment.

The main issue, in my mind, is setting up a Flush configuration that requires so many reaction path increments that even minor changes in solvent mass will lead to the result you are observing.

Hope that helps,

Tom

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