Three petrophysical classes are defined when data from limestone and dolomite rock fabrics are combined. The fabrics that make up the Class 1 field are (1) limestone and dolomitized grainstones and (2) large crystalline (>100 microns) grain-dominated dolopackstones and mud-dominated dolostones. The upper grain size limit of 500 microns is not well defined. An upper limit to this permeability field is imposed because as the grain size increases the slope of the porosity-permeability transform approaches infinity and porosity has little relationship to permeability.

Fabrics that make up the Class 2 field are (1) grain-dominate packstones, (2) fine to medium crystalline grain-dominated dolopackstones, and (3) medium crystalline mud-dominated dolostones.

Fabrics that make up the Class 3 field are characterized by mud-dominated fabrics (mud-dominated packstone, wackestone, and mudstone) and fine crystalline mud-dominated dolostones.

Each class is characterized by a specific porosity-permeability transform and porosity-saturation-reservoir height equation based on capillary pressure data. Reduced major axis (RMA) porosity-permeability transforms are presented below for each petrophysical class. The transform for the Class 2 field is slightly skewed to the field boundaries and a transform that is more compatible with the field boundaries is presented and recommended:

• Class 1 k = (45.35 x 10⁸) x ¯ip^8.537 | r = 0.71
• Class 2 k = (1.595 x 10⁵) x ¯ip^5.184 | r = 0.80 (recommended Class 2 k = (2.040 x 10⁶) x ¯ip^6.38)
• Class 3 k = (2.884 x 10³) x ¯ip^4.275 | r = 0.81

To quantify the saturation characteristics of the three petrophysical classes, capillary pressure curves with different interparticle porosities from each classes are compared. Each group of curves is characterized by similar displacement pressures and a systematic change in curve shape and saturation characteristics with changes in interparticle porosity. Equations relating water saturation to porosity and reservoir height are developed using a multiple linear regression with the log of water saturation as the dependent variable and the logs of capillary pressure and porosity as independent variables. Mercury capillary pressure is converted to reservoir height using generic values.

• Class 1: Sw = 0.02219 x H^-0.316 x ¯^-1.745
• Class 2: Sw = 0.1404 x H^-0.407 x ¯^-1.440
• Class 3: Sw = 0.6110 x H^-0.505 x ¯^-1.210

Interparticle Pore Space Classification | Petrophysics of IPS Data and Classes | Vuggy Pore Space Classification | Petrophysics of VPS Data

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