Problem 17. The oil from a volumetric undersaturated reservoir has a formation volume factor is 1.4 bbl/STB. The water saturation is 19 percent. 6 percent of the oil is produced and the new FVF is 1.45. The remaining gas saturation percentage is closest to: (A) 0.1 (B) 1 (C) 5 (D) 25.
This is a simple plug-and-chug problem with the needed equation. However, it's not common. 13 RES 4 has the equations you need:
Oil saturation = (1 – 0.06)(1 – 0.19)(1.45/1.4) = 0.788
Gas saturation = 1 – So – Swi = 1 – 0.788 – 0.19 = 0.021, or 2.1%, or (B).
First, one needs to know the proper equation. Noting the givens: undersaturated reservoir, the percentage produced, and appropriate formation volume factors should clue all you in.
Next, the answer is calculated as decimal...yet it asks for percentage with the decimal as an option. Not nice.
Finally, it doesn't give the exact match but makes you wonder. Rare, but it can happen, so double checking your work at all times is all one can do.
