Estimating elastic properties of carbonate samples from digital images

Dual energy coarse-resolution computed tomography (CT) scans reveal the density and atomic number volumes in carbonate samples. The atomic number volumes are resolved for the calcite and dolomite mineralogy volumes. These mineralogy and density volumes are converted into the total porosity volumes. To convert these mineralogy and porosity volumes into the effective elastic properties, we require a rock physics model relating the elastic bulk and shear moduli to porosity and mineralogy. Such a model is established by analysing wireline data from a well drilled in the oil field under examination. Two effective-medium models are established for these wireline data: the constant cement model and the differential effective medium model. To match the data, we found the coordination number and shear correction factor in the first model and the inclusion aspect ratio in the second model. In addition, we found the zero-porosity elastic property end points - bulk and shear moduli of pure calcite to match the wireline data. Both rock physics models were applied to the porosity and mineralogy volumes. This methodology offers ways of estimating the velocities in wells where wireline data are not available, e.g., horizontal wells or in legacy wells where rock material has been preserved.