Отправлено: 30.04.15 05:47. Заголовок: MODELLING AND INVERSION OF ELASTIC WAVE VELOCITIES AND ELECTRICAL CONDUCTIVITY IN CLASTIC FORMATIONS

MODELLING AND INVERSION OF ELASTIC WAVE VELOCITIES AND ELECTRICAL CONDUCTIVITY IN CLASTIC FORMATIONS WITH STRUCTURAL AND DISPERSE SHALES.
A. Aquino-LЁ®pez1, A. Mousatov1, M. Markov1, and E. Kazatchenko

Journal of Applied Geophysics (2015)

Abstract
This paper presents a new approach for simulating P- and S- wave velocities, and electrical
conductivity in shaly-sand rocks and determining the shale spatial distribution (disperse
and/or structural shale). In this approach, we used the effective medium method and
hierarchical model for clastic formations. We treat shaly-sand formations as porous naturalcomposite
materials containing: solid grains (such as quartz, feldspars and structural shale)
and pores completely filled with a mixture of hydrocarbon, water and disperse shale. For
calculating the effective elastic properties and electrical conductivity of this composite, we
have applied the multicomponent self-consistent effective media approximation (EMA)
method. We simulate the elastic velocities and electrical conductivity for clastic formations
in two steps. Firstly, we calculate the effective properties of mixture (combination of water,
hydrocarbon and disperse shale) filling the pores. Then we find the effective elastic and
electrical conductivity properties of formation constituted of solid grains (quartz and
structural shale) and pores with the effective properties determined in the previous step. We
considered that all components are represented by ellipsoids. The aspect ratios (shapes) of
grains and pores; are defined as a porosity function obtained for the model of clean sand
formations. Modelling results have demonstrated that the shapes of both shale components
(disperse and structural) weakly affect the effective elastic velocities and electrical
conductivity of shaly-sand formation and can be approximated by flatted ellipsoids. The
model proposed has been used to determine the volumes of disperse and structural shales
for two sets of published experimental data obtained from the cores. For determining the
shale distribution, we have performed the joint inversion of the following physical
properties: P-, S- wave velocities, total porosity, and total shale volume. Additionally, we
have predicted the effective electrical conductivity for the second set of data, taking into
account the shale distribution obtained by the inversion process. A good agreement
between the simulated effective conductivity and measured data confirms the determination
of shale spatial distribution, and allows us to validate the proposed model and calculation
technique.
Research Highlights
We propose a new petrophysical model for shaly sands.
We propose an approach for determining the shale spatial distribution
This approach is based on the effective medium method and hierarchical model.
For shaly-sand formations we have applied two-step homogenization.
We have simulated elastic velocities and electrical conductivity for clastic rocks.


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