HR: 0800h
AN: MR31C-0525    [Abstracts]
TI: Acoustic Properties of Carbonate Rocks and Their Relation with Porosity and Mineral Composition
AU: * Scotellaro, C
EM: cinzia@stanford.edu
AF: Stanford University, Rock Physics Laboratory Department of Geophysics 397 Panama Mall, Stanford, CA 94305, United States
AU: Vanorio, T
EM: tvanorio@pangea.stanford.edu
AF: Stanford University, Rock Physics Laboratory Department of Geophysics 397 Panama Mall, Stanford, CA 94305, United States
AU: Mavko, G
EM: mavko@stanford.edu
AF: Stanford University, Rock Physics Laboratory Department of Geophysics 397 Panama Mall, Stanford, CA 94305, United States
AB: Carbonates are complex rocks characterized by a wide range of facies, texture, micro-structure, and rock fabrics. Understanding how this complexity affects the acoustic properties of carbonates is a key issue for interpreting and predicting changes in seismic images and acoustic log. Questions arise from the study of the porosity versus velocity relation for carbonate rocks which often consider the large scatter around the main velocity-porosity trend predominantly related to the porosity. We started a comprehensive laboratory study on carbonate rocks to understand how mineral composition, together with porosity, controls seismic wave propagation. The samples were collected capturing a wide range of porosities (from 1-52 percent) and different depositional environments in order to represent at best pore fabric and mineralogical heterogeneity in carbonates. Results of the hydraulic, transport, and acoustic properties of the collected samples were compared with those reported in the literature. The main results of this research show that a quite heterogeneous mineral composition of the samples (calcite, dolomite, and anhydrite), other than the pore type, controls the elastic behavior of carbonate rocks, and thus, the velocity-porosity trend. In particular, the samples showing the biggest departure from the general velocity-porosity trend show a non-negligible amount of anhydrite. Compared to calcite, anhydrite 1) causes rock softening and in turn, a decrease of P-wave velocity, because of the lower bulk modulus (k =56 GPa); 2) is characterized by a finer grain size (silt-size) which may create two elastic domains separated by a critical porosity approximately 30 percent.
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
DE: 5102 Acoustic properties
DE: 5112 Microstructure
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting