* Change in water volume = –''NB''<sub>oi</sub>''S''<sub>wi</sub>/(1 – S<sub>wi</sub>)''c''<sub>w</sub>''P'' – ''W''<sub>e</sub> + ''W''<sub>p</sub>''B''<sub>w</sub>, due to connate water volume change, encroached water, and produced water | * Change in water volume = –''NB''<sub>oi</sub>''S''<sub>wi</sub>/(1 – S<sub>wi</sub>)''c''<sub>w</sub>''P'' – ''W''<sub>e</sub> + ''W''<sub>p</sub>''B''<sub>w</sub>, due to connate water volume change, encroached water, and produced water |