WELCOME  TO CRAIN'S PETROPHYSICAL HANDBOOK Please be fair to the author. Pay your Shareware fee HERE, and receive the CD-ROM at no extra cost. PERMEABILITY FROM POROSITY  Permeability from Porosity PERMp - Permeability from Porosity       1: PERMp = 10 ^ (HPERM * PHIe + JPERM)       2: IF PERMp > 20000       3: THEN PERMp = 20000 WHERE:   JPERM = permeability constant (fractional)   HPERM = porosity exponent (fractional)   PERMp = calculated permeability (millidarcies)   PHIe = effective porosity (fractional) COMMENTS: Because a poor choice of HPERM could create very large values of permeability, the computation is usually constrained to prevent unreasonable answers. Results have been very good in low and high porosity when calibrated to core. You can fit a regression line to anything - look at the graph and check the R-squared to confirm that the regression line is rational. RECOMMENDED PARAMETERS: ROCK TYPE                HPERM            JPERM Carbonates   chalky                         10 - 20               -2.5   fine sucrosic or   intercrystalline            20 - 30                -2.5   coarse sucrosic or   intercrystalline            25 - 50               -2.5   small vuggy                 30 - 100             -2.5   large vuggy                  50 - 200             -2.5   fractures 200 -                  300                 -3.0 Sandstones   very fine grains            10 - 20                -3.0   fine grains                    15 - 25                -3.0   medium grains             20 - 30                -3.0   large grains                  25 - 50                -3.0   conglomerate               20 - 50                 -3.0   unconsolidated             20 - 50                 -3.5   fractures                      200 - 300                -3.0 Permeability from Porosity - example of a "good" regression line. NUMERICAL EXAMPLE Assume data from Classic Example Sand B. PHIe = 0.30 SWir = Sw = 0.25 1. Wylie-Rose formula / Morris-Biggs parameters: CPERM = 62500 DPERM = 6.0 EPERM = 2.0 PERMw = 62500 * (0.30 ^ 6) / (0.25 ^ 2) = 730 md 2. Wylie-Rose formula / Timur parameters: CPERM = 3400 DPERM = 4.4 EPERM = 2.0 PERMw = 3400 * (0.30 ^ 4.4) / (0.25 ^ 2) = 272 md Permeability from Formation Factor PERMf - Permeability from Formation Factor       4: F = A / (PHIe ^ M)       5: PERMf = FPERM / (F ^ GPERM) WHERE:   A = tortuosity exponent (fractional)   FPERM = permeability constant (fractional)   GPERM = porosity exponent (fractional)   F = formation factor (fractional)   M = cementation exponent   PERMf = calculated permeability (millidarcies)   PHIe = effective porosity (fractional) COMMENTS: This formula has not been as successful as the Wylie - Rose approach. RECOMMENDED PARAMETERS: ROCK TYPE               FPERM              GPERM   Sandstone             7.0 * 10 ^ 6              4.5   Limestone             4.0 * 10 ^ 6              3.5 Data from individual core studies varies considerably from these average values. NUMERICAL EXAMPLE Assume data from Classic Example Sand B. PHIe = 0.30 A = 0.62 M = 2.15 Formation factor method: FPERM = 7.0 * 10 ^ 6 GPERM = 4.50 F = 0.62 / (0.30 ^ 2.15) = 8.25 PERMf = 7.0 * 10 ^ 6 / (8.25 ^ 4.5) = 526 md Copyright © E. R. (Ross) Crain, P.Eng.  email Read the Fine Print