Digital rock analysis (DRA) is a combination of experimental and numerical studies that helps to evaluate fluid transport and petrophysical properties at pore scale. We describe a concept of rigorous digital rock technology validation and present its workflow and application for a collection of reservoir rocks representing different lithologies, grain size and sorting, porosities, and permeabilities. The objective was to obtain relative permeability curves from a wide range of rocks (porosities ranging from 13% to 22% and absolute permeabilities from 3 to 570 md) using a direct hydrodynamic simulator that is based on the principles of density functional hydrodynamics and to verify the obtained results through a comparison with experimentally obtained relative permeability data.

Critical to the study was the separation between laboratory experimental procedures, performed by an energy company, and the digital experiments on the provided core imaging and fluid data performed by an energy technology service company. Each respective part of the study was performed independently, and data verification happened once both digital and physical data were obtained. The study was conducted in three phases. First, routine core analysis properties were established using DRA and experimentally. Second, a set of steady-state relative permeability digital experiments was performed using provided fluid data, flow rate, and P/T conditions that replicated experimental laboratory tests. Digital experiments were performed considering water-wet and mixed-wet scenarios. Third, a further sensitivity study compared basic (resolved meso- and micropore porosity) and advanced (resolved porosity plus submicron porous matrix and solid rock components) models to evaluate the effect of submicron porosity on multiphase transport properties.

All three phases were executed for each reservoir rock, and results were compared with independently obtained experimental data. An excellent match was observed on all studied rocks. Digital rock technology was proven to be a reliable technology for all studied rocks providing accuracy levels that are within the range of uncertainty of repeated laboratory test results on same core.

If applied in combination with the traditional laboratory analyses, DRA allows for a reduction of the cost and time for the petrophysical characterization of the rock and provides a better understanding of the transport mechanisms at the smallest scales.

You can access this article if you purchase or spend a download.