$5\mathrm{.}4$ Estimate the total reservoir compressibility for a sandstone formation that is char$-$

acterized by a porosity of $25\%.$ The reservoir is undersaturated $($i$.$e$.,$ no initial gas

cap is present$),$ and the oil and water saturations are $70\%$ and $30\%,$ respectively. The

compressibility of oil and water is $7\mathrm{.}5{10}^{-5}{}^{-1}$ and $2\mathrm{.}5{10}^{-5}{}^{-1},$ respectively.