Abstract
Measurement of drainage relative permeability by the centrifuge method was first introduced by Hagoort (SPE J. 29(3):139–150, 1980). It has been shown that capillary end effects can cause error in the measurement of relative permeability if a minimum rotational speed is not honoured. To determine the minimum rotational speed that makes the capillary end effect negligible, ω min, we propose that the value of capillary-gravity number, N cg, should be of the order of 10−2 or smaller. This conclusion is based on the use a Forward–backward scheme consisting of a forward numerical simulator developed for centrifuge experiments and applying Hagoort’s method as a backward model. The article presents the use of this Forward–backward scheme as a powerful tool for error analysis such as determining the impact of capillary end effects. By using this loop, we first determine ω min for specific core and fluid properties. Later, we generalize the ω min calculations by using the definition of N cg as a “rule of thumb” for designing relative permeability experiments by centrifuge method. We also demonstrate another use of this loop for controlling the quality of the experimental data.
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Abbreviations
- g c :
-
Average centrifugal acceleration [LT−2]
- k rw :
-
Relative permeability of the wetting phase, fraction
- \({k^\prime_{\rm rw}}\) :
-
Derivative of the wetting phase relative permeability, fraction
- k rwD :
-
Relative permeability of the wetting phase, normalized
- \({k_{\rm rw}^o }\) :
-
End point value of the wetting phase relative permeability, fraction
- L :
-
Length of the core sample [L]
- n :
-
Corey exponent, dimensionless
- n :
-
Number of data points in error calculations
- N B :
-
Bond number, dimensionless
- N cg :
-
Capillary-gravity number, dimensionless
- N p :
-
Pore volume cumulative production, dimensionless
- P c :
-
Capillary pressure [ML−1T−2]
- P cth :
-
Threshold capillary pressure [ML−1T−2]
- P cD :
-
Capillary pressure, dimensionless
- r m :
-
Distance of center of the rotation to middle of the core [L]
- r o :
-
Distance of center of the rotation to the core inlet [L]
- S wD :
-
Wetting phase saturation, normalized
- S wDe :
-
Wetting phase saturation at core exit, normalized
- t :
-
Time [T]
- t D :
-
Time, dimensionless
- x :
-
Length in x-direction [L]
- x D :
-
Length in x-direction, dimensionless
- β(t):
-
Time function of the rotational speed, dimensionless
- \({\phi}\) :
-
Porosity, fraction
- Δρ :
-
Density difference [ML−3]
- ω :
-
Rotational speed (rpm)
- ω 1 :
-
Initial rotational speed (rpm)
- ω min :
-
Required rotational speed in relative permeability experiments (rpm)
- μ w :
-
Wetting phase viscosity [ML−1T−1]
- σ :
-
Surface tension [MT−2]
- N B :
-
= kΔρω 2 r m/σ
- N cg :
-
\({=\dfrac{P_{\rm cth}}{\Delta \rho gL},N_{\rm cg} =\dfrac{P_{\rm cth}}{\Delta \rho \omega^{2}r_{\rm m} L}}\)
- S wD :
-
\({=\dfrac{S_{\rm w} -S_{\rm wir}}{1-S_{\rm wir} -S_{\rm gc}}}\)
- t D :
-
\({=\left( {\dfrac{kk_{\rm rw}^o}{{\rm \mu}_w}\Delta \rho \omega_{1}^{2} r_o}\right)\dfrac{t}{L\phi \left( {1-S_{\rm wir} -S_{\rm gc}}\right)}}\)
- β (t ):
-
\({=\,\left\{ \begin{array}{l@{\quad}l} 0 & {\rm t} < 0 \\ 1 & 0\leq {\rm t} \leq {\rm t}_1 \\ \left(\frac{\omega_j}{\omega_1} \right)^{2} & {\rm t}_{j-1} \leq {\rm t} \leq {\rm t}_{\rm j} \end{array} \right.}\)
- P cD :
-
\({=\dfrac{P_c}{P_{\rm cth}}}\)
- k rwD :
-
\({=\dfrac{k_{\rm rw}}{k_{\rm rw}^o}}\)
- x D :
-
\({=\dfrac{x}{L}}\)
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Saeedi, M., Pooladi-Darvish, M. Revisiting the Drainage Relative Permeability Measurement by Centrifuge Method Using a Forward–backward Modeling Scheme. Transp Porous Med 86, 49–71 (2011). https://doi.org/10.1007/s11242-010-9605-9
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DOI: https://doi.org/10.1007/s11242-010-9605-9