Rock and fluid analysis services in the laboratory and at the wellsite
Comparison of the fluid arrangement evolution measured in fast synchrotron micro-CT experiments on two rock types to quasi-static simulations which implement capillary-dominated pore filling and snap-off, including a sophisticated model for cooperative pore filling.
The results indicate that such pore network models can, in principle, predict fluid distributions accurately enough to estimate upscaled flow properties of strongly wetted rocks at low capillary numbers.
Three-dimensional X-ray computed tomography was used to characterize the pore structure of the reservoir core. We obtained in-situ pore-scale images of the distribution of CO2: brine analogue fluid pairs within reservoir samples during low capillary number drainage and imbibition flooding experiments. The micro- CT images are used directly as input to a pore-scale simulation model. The validity is investigated by comparing on a pore-by-pore basis the simulated and imaged fluid distributions. The pore filling states are in good agreement both for drainage and imbibition displacements and the computed capillary trapping curve agrees with experimental data.
A pore-network model study of capillary trapping in water-wet porous media was presented. The amount and distribution of trapped non-wetting phase is determined by the competition between two trapping mechanisms - snap-off and cooperative pore-body filling. A new model to describe the pore- body filling mechanism in geologically realistic pore-networks was developed. The model accounts for the geometrical characteristics of the pore, the spatial location of the connecting throats and the local fluid topology at the time of the displacement, which was validated by comparing computed capillary trapping curves with published data for four different water-wet rocks. Computations were performed on pore-networks extracted from micro-CT images and process-based reconstructions of the actual rocks used in the experiments. Compared with commonly used stochastic models, the new model describes more accurately the experimental measurements, especially for well connected porous systems where trapping is controlled by subtleties of the pore structure. The new model successfully predicts relative permeabilities and residual saturation for Bentheimer sandstone using in-situ measured contact angles as input to the simulations. The simulated trapped cluster size distributions are compared with predictions from percolation theory.