Sum the Volumes

Part 15, Chapter 15: The Complete Build, End to End

From Rock to Oil

The static model is built; now count the oil. The oil-water contact splits the net sand into an oil column above and a water leg below. The oil-filled pore volume, summed over the column and divided by the formation volume factor, is the stock-tank oil in place (STOIIP), the volume every development hangs on.

Move the Contact

Lowering the contact thickens the oil column and grows the STOIIP, up to the point where the structure spills. The contact is one of the most uncertain and most consequential inputs, so a careful study brackets it rather than trusting a single depth.

Robust to the Grid

Change the resolution and the STOIIP barely moves: an in-place volume is a sum over the rock, and a sum is robust to the grid. The flow that comes next is not, which is why the cell count mattered for the framework and will matter again for the flood.