Probing the 3D molecular and mineralogical heterogeneity in oil reservoir rocks at the pore scale

Innovative solutions have been designed to meet the global demand for energy and environmental sustainability, such as enhanced hydrocarbon recovery and geo sequestration of CO2. These processes involve the movement of immiscible fluids through permeable rocks, which is affected by the interfacial properties of rocks at the pore scale. Overcoming major challenges in these processes relies on a deeper understanding about the fundamental factors that control the rock wettability. In particular, the efficiency of oil recovery strategies depends largely on the 3D wetting pattern of reservoir rocks, which is in turn affected by the adsorption and deposition of contaminant molecules on the pores surface. Here, we combined high resolution neutron tomography NT and synchrotron X ray tomography XRT to probe the previously unobserved 3D distribution of molecular and mineralogical heterogeneity of oil reservoir rocks at the pore scale. Retrieving the distribution of neutron attenuation coefficients by Monte Carlo simulations, 3D molecular chemical mappings with micrometer dimensions could be provided. This approach allows us to identify co localization of mineral phases with chemically distinct hydrogen containing molecules, providing a solid foundation for the understanding of the interfacial phenomena involved in multiphase fluid flow in permeable medi

Simulating thermohydrodynamics by finite difference solutions of the Boltzmann equation

The formulation of a consistent thermohydrodynamics with a discrete model of the Boltzmann equation requires the representation of the velocity moments up to the fourth order. Space-filling discrete sets of velocities with increasing accuracy were obtained using a systematic approach in accordance with a quadrature method based on prescribed abscissas (Philippi et al., Phys. Rev. E, 73 (5), n. 056702, 2006). These sets of velocities are suitable for collision-propagation schemes, where the discrete velocity and physical spaces are coupled and the Courant number is unitary. The space-filling requirement leads to sets of discrete velocities which can be large in thermal models. In this work, although the discrete sets of velocities are also obtained with a quadrature method based on prescribed abscissas, the lattices are not required to be space-filling. This leads to a reduced number of discrete velocities for the same approximation order but requires the use of an alternative numerical scheme. The use of finite difference schemes for the advection term in the continuous Boltzmann equation has shown to have some advantages with respect to the collision-propagation LBM method by freeing the Courant number from its unitary value and reducing the discretization error. In this work, a second order Runge-Kutta method was used for the simulation of the Sod's shock tube problem, the Couette flow and the Lid-driven cavity flow. Boundary conditions without velocity slip and temperature jumps were written for these discrete Boltzmann equation by splitting the velocity distribution function into an equilibrium and a non-equilibrium part. The equilibrium part was set using the local velocity and temperature at the wall and the non-equilibrium part by extrapolating the non-equilibrium moments to the wall sites

Evaluation of the conventional and synchrotron X ray tomography applied to heterogeneous oil reservoir rocks

Carbonate and sandstone reservoirs play an important role in oil industry as they host over 50 of the world s hydrocarbon reserves. For an accurately assessment of porosity and pore size distribution of such complex pore network, which affect directly the macroscopic characteristics of multiphase fluid flow, X ray computed microtomography micro CT emerges as a powerful tool. In contrast to lab based X ray micro CT XCT , synchrotron X ray micro CT SXCT images are commonly free of artefacts i.e. beam hardening and the unique properties of synchrotron sources enable the X ray imaging of complex and heterogeneous materials in greater detail, with higher quality, and short acquisition time. This work reports results of cone beam computed microtomography XCT in comparison with synchrotron computed microtomography SXCT applied to very heterogeneous carbonate and sandstone reservoir rocks. We analyze the quality of the image generated in terms of detection of details and artefacts, the advantages and limitation of each technique, as well as features like contrast, sharpness, and signal to noise ratio SNR . Although SXCT offers significant advantages over XCT, the latter gains in cost of operation, accessibility and user friendlines