A Workflow to Analyze Vertical Formation Heterogeneity and Optimum Geological Grid Layering Using Petrophysical Logs

Abstract

Integrated, multidisciplinary field projects require the transfer of large datasets and results from one discipline to another. Typically, petrophysical workflows for geological modeling produce only rock-types, porosity, permeability, and water saturation model logs. Petrophysical logs are upscaled to the fine geological model grid during the 3D modeling workflow. The geological model aerial cell dimensions and layer size are determined using geostatistical methods to optimize the run time during the dynamic simulation phase. In this study, we propose to enhance the number of outputs from the petrophysical workflow by providing recommendations on the optimal vertical layer size by stratigraphic interval for capturing all relevant heterogeneities associated with complex carbonate reservoirs. We assume that the deflections of the petrophysical logs (such as porosity or permeability) are symmetrical across the geological layer. This is a reasonable assumption for vertical and subvertical wells since the layer size should be comparable to the vertical resolution of the logs. Therefore, the inflexion points of the input log correspond to the facies changes. After identifying the layers’ borders, we calculate the thickness of each layer and its corresponding input log value. The developed application was successfully tested using data from more than 200 wells of a giant carbonate reservoir from the Middle East. The results demonstrate that the developed algorithm parameters are easily adaptable to a variety of both different input log types and various ranges of petrophysical properties. The created interface interactivity enables the user to readily assess and alter parameters to optimize the layering scheme while capturing the right level of heterogeneities. During the testing on a real dataset, the developed application revealed vital information on the formation's vertical heterogeneity and the significant difference between distinct stratigraphic intervals. The provided analysis of layer thicknesses can be used directly for the creation of static model layering scheme.