Two-Point Determinations of Permeability and PV vs. Net Confining Stress

Summary Empirical equations are presented that accurately fit permeability, PV, or porosity data vs. net confining stress. Each of these equations has four adjustable parameters. With little loss of accuracy, however, two of the coefficients can be preset. Consequently, permeability, PV, or porosity measurements need to be made at only two confining stresses—e.g., at 1,500 and 5,000 psi [10.3 and 34'.5 MPa] to define the stress dependence within close tolerances completely. With the techniques described, economical measurements of these stress-dependent properties can be made on a routine basis. The results can be used to calculate PV compressibility and to estimate productivity declines resulting from permeability reduction as deep, high-pressure reservoirs are drawn down.