On a Capillary Pressure in Two-Phase Reservoirs

Abstract

An equilibrium state of geothermal fluid in fractured and/or porous reservoirs is discussed, when classic hydrostatic equation, as corollary of Darcyís law, gives wrong results. It is shown, that generally hydrostatic equation must include addition term, which eliminates considered paradox of incomplete physical model. The use of modified hydrostatic equations can increase adequacy of calculation of fluid pressure both in one-phase saturated and two-phase (unsaturated two-component) geothermal reservoirs. The two-phase modification of hydrostatic equation eliminates known negative absolute fluid pressure paradox for unsaturated permeable medium (two-phase geothermal reservoir), followed from standard hydrostatic equation and gives simplified correlations between capillary pressure and fluid saturation, which satisfactorily compare with laboratory experimental data for porous media.