Gas Reservoir MBE: 2016 #17

A gas reservoir produced 1 MMscf gas, 10 MSTB water, and had 1,100 bbl water influx. 
Current & initial gas FVFs are...water FVF... IGIP:

These problems are easy minus unit confusion issues. You can't be too careful with units here:

= (1,000 Mscf)(1.1 RB/Mscf ) + 10,000 RB – 1,100 RB
= 1,100 RB + 10,000 RB -1,100 RB = 10,000 RB
= 10,000 RB/(1.1 – 1 RB/Mscf)
= 10,000 RB/(0.1 RB/Mscf)
= 100,000 Mscf, or (B).