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Line 138: − − where Vp is the P-Wave velocity and Vs is the S-Wave velocity. According to Castagna et al (1985), Vp and Vs can be calculated by using this formula: + + + +
Well log analysis for reservoir characterization (view source)
Revision as of 20:45, 8 December 2014
, 20:45, 8 December 2014→Calculate the Elasticity
==Calculate the Elasticity==
==Calculate the Elasticity==
There are so many kinds of elastic properties of a rock, there are Acoustic Impedance (AI), Shear Impedance (SI), Poisson Ratio (σ), etc. and most of them depend on the wave velocity and density.
There are so many kinds of elastic properties of a rock, there are Acoustic Impedance (AI), Shear Impedance (SI), Poisson Ratio (σ), etc. and most of them depend on the wave velocity and density.
:<math>AI = \rho \times V \rho</math>
:<math>AI = \rho \times V \rho</math>
:<math>SI = \rho \times Vs</math>
:<math>SI = \rho \times Vs</math>
:<math>\sigma = \frac{\left (\frac{Vp}{Vs} \right )^2 - 1}{2 \left(\frac{Vp}{Vs} \right )^2 - 1}</math>
:<math>\sigma = \frac{\left (\frac{Vp}{Vs} \right )^2 - 1}{2 \left(\frac{Vp}{Vs} \right )^2 - 1}</math>
where Vp is the P-Wave velocity and Vs is the S-Wave velocity. According to Castagna et al (1985), Vp and Vs can be calculated by using this formula:
:<math>Vp (km/s) = 5.81 - 9.42 \times \mathit{\Phi} s - 2.21 \times Vclay</math>
where φs is the sonic-derived porosity, Vclay is the clay volume, Δtlog is the sonic log reading (DT), Δtmatrix is the matrix transit time (see table 4 for reference value), and Δtfluid is the fluid transit time (see table 4 for reference value). Theoretically, a formation with high density will has lower transit time (Δtlog) which will cause the seismic wave to travel faster in that formation. An anomaly in density and sonic log (Δt) in a formation may indicates the presence of fluids in that formation (see section 9).
where φs is the sonic-derived porosity, Vclay is the clay volume, Δtlog is the sonic log reading (DT), Δtmatrix is the matrix transit time (see table 4 for reference value), and Δtfluid is the fluid transit time (see table 4 for reference value). Theoretically, a formation with high density will has lower transit time (Δtlog) which will cause the seismic wave to travel faster in that formation. An anomaly in density and sonic log (Δt) in a formation may indicates the presence of fluids in that formation (see section 9).