| Popis: |
This paper provides a new computational rock physics study of middle east carbonate rock. Computed elastic and electrical properties from real rock micro-tomographis and constructed 3D sphere packs build direct link between rock microstructure and its elastic, electrical responses. Multi-resolution CT scans (resolution varying from nanometer to micron) are taken for carbonate core samples belonging to different facies from middle east carbonate reservoirs. Different carbonate petrophysical pore types shows clearly different pore structures (pore shape, size, connectivity). Laplace equation and linear Stokes equation are directly solved on those 3D rock micro-tomographis to compute electrical conductivity and hydraulic permeability using finite difference method (FD). Elastic properties (Vp, Vs, bulk modulus, shear modulus, Young's modulus and Poisson's Ratio) are computed by solving linear stress-strain relationship using finite element method (FEM). To further extend predicting capability, a family of 3D model granular porous media with different porosity, pore (grain) aspect ratio, pore (grain) size distribution, pore connectivity and spatial arrangement are built to represent different carbonate petrophysical pore types. Results for different carbonate facies (Wackestone with roundish micropore system (microporosity); Grainstone, Packstone with interpartical pore (IP) system; Rudstone with vuggy porosity and IP frame) are shown. Measurements on core plugs compare well with modeling results and computed values. We can rigorously determine the pore geometry related parameters in effective medium based model (Xu-Payne model) from numerical computation to interpret and predict log response for upscaling. Finally, AVO seismic forward modeling is built to quantify porosity, fluid saturation and lithology (facies) effect on seismic response for middle east carbonate reservoir. A complete study at pore and core scale, log scale to seismic scale is achieved. Conclusions and recommendations on inverting porosity, fluid saturation and carbonate facies from pre-stack seismic in carbonate reservoir are given at the end. |
