Velocity–porosity–mineralogy trends in chalk and consolidated carbonate rocks

Abstract

SUMMARY Published laboratory elastic-wave velocity versus porosity data in carbonate rocks exhibit significant scatter even at a fixed mineralogy. This scatter is usually attributed to the strong variability in the rock-frame or pore-space geometry, which, in turn, is driven by the richness and complexity of diagenetic alteration in these very reactive sediments. Yet, by examining wireline data from oil-bearing high-to-medium porosity chalk deposits, we find surprisingly tight velocity–porosity trends. Moreover, these trends are continued into the low-porosity domain by data from a location thousands of miles away from the chalk field. This congruence implies a universality of diagenetic trends, at least in the massive deposits under examination. We also find that the elastic bulk and shear moduli of the pure-calcite end member are somewhat smaller than such values reported in the literature. Using the end-member elastic constants relevant to the data under examination, we establish a theoretical rock physics model to match and generalize these data.

Rock Physics: Recent History and Advances

“…Equations (17) and 18provide us with a fluid substitution recipe as follows. Assume that we know the bulk modulus K SatA of rock saturated with Fluid A whose bulk modulus is K fA and density is ρ fA .…”

“…The curves are from the stiff-sand model with the coordination number 6, differential pressure 30 MPa, critical porosity 0.40, and shear stiffness correction factor 1. The two model curves are for the two slightly different properties of the pure calcite end member (adopted from Dvorkin and Alabbad [17]). Although the aforementioned concept is simple, its implementation is not.…”

Elastic Properties of Pannonian Basin Limestone under Different Saturation Conditions

“…The results of Rafavich et al (1984) [2] are based on cores from a depth range of 1200 to 3100 m from the surface with confining pressure of 40 MPa, while the results of the current study are based on cores from a depth range of 805.24 to 974.11 m from the surface with different effective pressures. Such consistency in velocity-porosity trends have been discussed by [34] on studied wireline data of chalk despite very large distance to reservoir location. They conclude that diagenetic trends are universal in carbonates.…”

“…If we consider also results given by [5,7,33] correlation of Vp and Vs (Figure 16) with different confining pressure have credibility for defining the empirical relation defined with formula 1 and 2. Such consistency in velocity-porosity trends have been discussed by [34] on studied wireline data of chalk despite very large distance to reservoir location. They conclude that diagenetic trends are universal in carbonates.…”

Effect of heterogeneity on failure of natural rock samples

“…Finally, this porosity contrast was translated into the elastic-moduli contrast by assuming the stiff-rock effective-medium model described in, e.g., 10 . This model accurately describes the velocity-porosity wireline data from the well where the samples were extracted from (see 11 ).…”