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 A Study on Two Phase, Non-Darcy Gas Flow Through Proppant Packs
L. Jin, SPE, and G.S. Penny, SPE, STIM-LAB, Inc.
This study shows that the Forchheimer correlation does not adequately model multiphase flow. A laboratory experiment flowing the equivalent of 5 MMSCFD + 20 BWPD through a 50' frac height showed a factor of 35 reduction in effective conductivity. This equates to a 3% “retained perm”, even before embedment and gel damage. Figure 7 shows a factor of 75 reduction in permeability for oil-gas two phase flow versus dry gas. Even at low oil saturations, a factor of 10 reduction was observed.
The authors theorize that the liquid velocity may be 20 times the superficial velocity due to being dragged by the gas, and note that current production models fail to account for this effect. An alternative solution is proposed to correct single phase pressure drops for multiphase flow, as adjustments to beta (the inertial flow coefficient) were not satisfactory due to non-linearity in the correlation.
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