IMPROVED SCALING TECHNIQUE FOR 2-PHASE PRESSURE-SATURATION RELATIONSHIPS

Current methods of scaling imbibition and drainage pressure-saturation data scale the capillary pressure head using ratios of surface tensio n, constant intrinsic contact angle, fluid density difference and bubb ling pressure. These methods are applicable to scaling either the main drainage or imbibition curve for different fluid pairs. However, for a given fluid pair, scaling of the drainage to the imbibition curve is generally unsatisfactory. For the drainage to imbibition case, the ma ximum error in computed saturations typically occurs at saturations re presentative of the funicular zone. It is proposed that an empirical f unctional relationship between advancing and receding apparent contact angles for a specific porous medium can be used to improve the scalin g of imbibition to drainage pressure-saturation data for organic liqui d-water systems. The Leverett J scaling function is modified by includ ing the ratio of the apparent contact angles as a new scaling term. In the term cos (phi(R))/cos(phi(A))(p), the advancing apparent contact angle is first corrected for the combined effects of hysteresis and su rface roughness by a constant exponent p. The exponent p is equal to t he power of the fit of the advancing apparent contact angle, phi(A), t o the receding apparent contact angle, phi(R). The magnitude of the co rrection appears to be a characteristic of the medium; however, more l aboratory tests are needed for verification. The scaling procedure is tested for a limited series of fluid pairs in several porous media tha t are characterized by differing pore size distributions and granular compositions. The scaling technique is inadequate, however, for system s subjected to forced imbibition. (C) 1997 Elsevier Science B.V.