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Creates the rock physics model to be used in forward modeling Vp, Vs and density logs for different reservoir conditions. Derived attributes (relative properties and reflectivities) can be computed from the modeled logs at well-log or seismic resolutions and in time or depth domains.
The rock physics model is constituted by moduli and densities of the rock’s constituents and the effective media relationships that effectively reconstruct (model) the measured rock properties’ logs.
Well-log Inversion
The rock physics model is defined
- Effective media relationships are selected. Some options:
- Solid’s mixing relationship. i.e. Hill Average, Hashin-Shtrikman, other.
- Fluid’s mixing relationship. i.e. Wood, patchy, other
- Porosity inclusion. i.e. Krief, critical porosity, other
- Fluid inclusion. Gassmann’s equations
- Moduli and densities of rock constituents are estimated
- The required volume fractions of rock constituents are computed through a petrophysical (mineralogical) evaluation. These are an input to SeisRp (not computed within SeisRP).
- Moduli and densities of fluids are computed using Batzle and Wang equations
- Moduli and densities of solid constituents are computed in the well-log inversion program. In this program, moduli and densities are iteratively modified and Vp, Vs and density logs reconstructed. The final moduli and densities are those that result in the least difference between modeled and measured logs.
Once the rock physics model is defined, reservoir properties can be modified and Vp, Vs and density logs reconstructed as if they had been acquired under the modified condition
Well-log Modeling
Forward modeling of rock properties for varying reservoir properties
- Relative rock properties, absolute rock properties or reflectivities are computed for varying reservoir properties.
- Analysis is done at well-log or seismic resolutions and in time or depth.
- Reservoir properties are varied in percent of in-situ value, or as a range of constant volume fractions.
- Plots in time are done at the in-situ time-depth or at the two-way-time that results from modifying reservoir properties.
3D Model
The objective of the 3D Model module is to create datasets in which well-data is perturbed in target interval(s), and synthetic seismic computed for the perturbed well data. The pseudo well and synthetic seismic data created are used to evaluate/calibrate seismic inversions as well as to estimate seismic attributes’ sensitivity to changes in petrophysical properties.
Methodology to create the 3D Model
- Create a 3D volume of petrophysical properties from an evaluation in a well. Two of the properties are modified in inline and crossline directions (for example, porosity, in inline direction and mineralogy in the cross-line direction).
- Elastic Rock Properties (VP, VS) and density (r) are computed for each pseudo-well in the 3D volume.
- Seismic attributes are computed in time or depth, and at well-log or seismic resolutions.