A MODEL FOR WETTABILITY CHANGE IN RESERVOIR ROCK

ABSTRACT We have developed a model describing wettability change in reservoir rock after primary drainage. Wettability change is dependent on phenomena at several length scales: macroscopic parameters like drainage pressure and ageing time, and small scale interactions like molecular interactions between brine, rock and oil. The model for ageing involves three parameters, ageing time, drainage pressure and a characteristic pressure. The characteristic pressure reflects the wetting film properties; it depends on chemical properties of the oil, water and rock and is related to the disjoining pressure. It is found that a wettability change, qualitatively described by the Amott-Harvey index, can be obtained for a single core for different ageing time and drainage pressure

Numerical methods for the simulation of the settling of flocculated suspensions

For one space dimension, the phenomenological theory of sedimentation of floculated suspensions yields a model that consists of an initial-boundary value problem for a second order partial differential equation of mixed hyperbolic-parabolic type. Due to the mixed hyperbolic-parabolic nature of the model, its solutions may be discontinuous and difficulties arise if one tries to construct these solutions by classical numerical methods. In this paper we present and elaborate on numerical methods that can be used to correctly simulate this model, i.e., conservative methods satisfying a discrete entropy principle. Included in our discussion are finite difference methods and methods based on operator splitting. In particular, the operator splitting methods are used to simulate the settling of flocculated suspensions. (orig.)Available from TIB Hannover: RR 6943(99-03) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Capillary pressure correlation for mixed-wet reservoirs

Summary For water-wet reservoirs, several expressions may be used to correlate capillary pressure, or height above the free water level, with the water saturation. These correlations all feature a vertical asymptote at the residual water saturation where the capillary pressure goes to plus infinity. We have developed a general capillary pressure correlation that covers primary drainage, imbibition, secondary drainage, and hysteresis scanning loops. The graph exhibits an asymptote at the residual saturation of water and of oil where the capillary pressure goes to plus and minus infinity, respectively. The shape of the correlation is simple yet flexible as a sum of two terms, each with two adjustable parameters and is verified by laboratory experiments and well-log data. An associated hysteresis scheme is also verified by experimental data. The correlation can be used to make representative capillary pressure curves for numerical simulation of reservoirs with varying wettability and to model and interpret flooding processes

On some upwind schemes for the phenomenological sedimentation-consolidation model

SIGLEAvailable from TIB Hannover: RR 6943(2000,5) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Central difference solutions of the kinematic model of settling of polydisperse suspensions and three-dimensional particle-scale simulations

Available from TIB Hannover: RR 6943(2000,4) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Numerical simulation of the settling of polydisperse suspensions of spheres

The extension of Kynch's kinematical theory of ideal suspensions to polydisperse suspensions of spheres leads to a nonlinear system of conservation laws for the volumetric concentration of each species. In this work, we consider particle species different in sizes and densities, including the buyant case. We show that modern shock-capturing numerical schemes for the solution of systems of conservation laws can be employed as an efficient tool for the simulation of the settling and separation of polydisperse suspensions. This is demonstrated by comparison with published experimental and theoretical results and by simulating some hypothetical configurations. Particular attention is focused on the emergence of rarefaction waves. (orig.)Available from TIB Hannover: RR 6943(99-02) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman