In-Situ Investigation of Aging Protocol Effect on Relative Permeability Measurements Using High- Throughput Experimentation Methods
Résumé
Relative permeabilities are a first-order parameter to consider when describing multiphase flows in porous media. Among many other parameters, the core wettability controls the fluids repartition in the porous media at pore scale, strongly affecting how the fluids can be displaced (i.e., their relative permeabilities). As the initial wettability of cores sampling a reservoir is rarely preserved, classical SCAL measurements (such as relative permeabilities) may not reflect the rock properties at reservoir conditions. This original core wettability may be restored in a process referred as ‘core aging’. It is generally done by injecting the core with the reservoir fluids (brine and crude-oil) to equilibrate the rock surface with respect to the oil and brine components. Here, we investigated the effect of two aging protocols (static and dynamic) on wettability restoration, and characterize the aging using oil/water relative permeabilities measured on the core after aging. The two aging protocols were applied on a set of initially strongly water-wet outcrop sandstone samples (Bentheimer). The relative permeabilities were measured using the steady-state method and a state-of-the-art experimental setup (CAL-X) based on X-ray radiographies. The setup is equipped with an X-ray radiography facility, enabling monitoring of 2D local saturations in real time and thus giving access to fluid flow paths during the flooding. The relative permeability curves of aged samples show clear differences when compared to water-wet relative permeabilities, hence. suggesting that the wettability has been effectively altered. However, the two aging protocols were unable to produce the same results. The dynamic aging has led to an inversion of the original relative permeability curves asymmetry, suggesting a strongly oilwet system, whereas the static aging protocol has altered the wettability to a lesser extent. The differences can be explained by analyzing 2D saturation maps. In the case of dynamic aging we observed a homogeneous distribution of fluid saturation during fractional flow. In contrast, the static protocol results in heterogeneous flow paths, confirming that this protocol did not uniformly alter the wettability of the sample and generates a patchier mixed-wettability system.