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Calculating pore volume flushes using CCF data


deacon
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Hello,

Latest build of GMS 8.2, This is a steady state model. Using the 3D Data to 2D Data and 2D Data Set Calculator tools. The goal is to determing the pore flush of each cell in the model and then map that on the 2D grid.

I am trying to calculate pore flushes on a per cell basis. My approach is to determine the flow through each cell (ft3/dy * num_days * years) and then divide that by the pore volume of each cell (((Top - Bot) * area ) * porosity). Can you check the following as I am slightly perplexed as to how GMS is handling some of the data.

I am attempting to use the CCF data to accomplish this. When I convert the CCF file to data sets, I get Front, Right, Bottom (along with source sinks). I am assuming that this is because adjoining cells provide the other faces of data; e.g. one cell's left is another cell's right.

When I compare the data in these 2D data sets I see that the absolute values agree with what I am seeing in the flow budget option(s). However, there are some differences in negative and positives. I believe that converting the CCF to datasets loses/reverses some of the directionality (in (+) out (-)) that is carried in the flow budget. That is, we are only seeing the orientation and magnitude of flow from the perspective of the selected cell at the faces given. FInally, the sum of these data sets will equal the average daily flow through the cells (I am ignoring sources and sinks as there are none in my areas of interest, this is all cell to cell flow).

When I sum the cell to cell data sets (not including source sinks) the sum will be positive or negative depending on where the cell is in the model. My belief is that this does not carry is real physical meaning, just that the sum of those three faces in total is either positive or negative with repect to that cell and with three free variables we really cannot impart directionality at this point. I then take it that the absolute value of the summed data sets as the daily average flow through each cell.

Does that sound right?

So the process for calculating the pore volume of each cell is something like:

Use 3D -> 2D data to get tops and bottoms of each layer in model

Use 2D calculator to get pore volume for each cell

Use CCF -> Data Sets to get CCF for the three faces

Add the Front, Right, Bottom data sets for each layer (include source sinks as needed) to get total average flow for each cell

Use the 2D calculator to get absolute values for each cell

Multiply the Abs Value Sum dataset to get total time of interest (e.g. pore flushes over 10 years (3650 days))

Use 2D Data calulator to divide absolute value average flow dats set by pore volume data set

Graph results for map view.

Thanks in advance

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