f Combining seismic and petrophysics to improve facies proportions modeling

A new workflow to propagate expected Facies proportions from wells into the 3D space is proposed, considering seismic data as stronger constraints than a simple drift or auxiliary variable in cokriging calculations. The idea is to combine seismic attributes transformed into Porosity, calibrated to well data, with the Porosity distribution per Facies determined from core plugs and Porosity logs. The workflow is made of two steps, the first one corresponding to calculations at seismic vertical scale, the second one being a resolution enhancement at well data scale (between 1 meter and 1 foot). In the first step, well data are obviously averaged at seismic vertical scale for ensuring consistency between the different data sources. At this vertical scale, the average Porosity at a given location in the reservoir is obtained from a mixture of already defined Facies, which expected proportions are related to the Porosity distribution inside each Facies. The distribution of expected Facies proportions at any point is calculated, ensuring that the average Porosity calculated from seismic attributes at that point is honoured. Then, the vertical evolution of Facies proportions is calculated at a sub-metric scale, from well data and the local average proportions previously determined.