Deliverables Model for gas condensate relative permeability and critical condensate saturation as functions of the capillary number and the Bond number (far reservoir region) The objective was to propose a model for the relative permeabilities and the critical condensate saturation based on a physical description of the porous medium (geometry of the pore-space, rock permeability) and the fluid/rock interactions. A fractal model has been proposed to calculate gas condensate relative permeability and critical condensate saturation as functions of the capillary number and the Bond number, the dimensionless parameters expressing viscous to capillary and gravity to capillary forces ratios. The model takes into account the wetting/spreading characteristics of the system (rock & fluids). It also includes the structure characteristics of the porous medium through its fractal dimension. The model predicts the modification of the relative permeability curves as the capillary number changes (velocity or interfacial tension changes). A threshold condensate saturation, Stc, can be predicted below which the condensate mobility is extremely reduced, even though finite. Stc may be very high in highly fractal (very clayey) sandstones. It decreases with increasing capillary number. The critical saturation for condensate mobility, Scc, increases with increasing interfacial tension and fractal dimension. A very satisfactory agreement between model prediction and experimental results was obtained. It is demonstrated that apparently contradictory laboratory results on the dependence on interfacial tension and flow rate separately considered can be reconciled. This model will be implemented in a reservoir simulator in the near future. Model for high flow rate effect on gas condensate relative permeabilities (near well-bore region) Examination of different approaches to model high flow rate effects. Modelling of the experimental results depends on the definition of gas relative permeability. The most promising approach was to model inertial flow effects separately through the non-Darcy flow factor FND, in which case the relative permeability could be modelled as a function of capillary number. The relative permeability data could be fitted either through a correlation of krg as a function of capillary number and the ratio krg/kro, or by a correlation of krg and kro as functions of saturation and capillary number. The model for krg and kro in terms of saturation and capillary number gave fair agreement with the in-situ saturation measurements. The model supported the observation of condensate saturation increasing with capillary number at a fixed value of the ratio krg/kro. The Whitson-Fevang 2-parameter model gives a reasonable match to the high-rate data. Therefore, this correlation should provide a reasonable 'first guess' of the capillary number effect where no measured data are available. These results could be used in a pseudo-pressure calculation to estimate well productivity, but only if the simulation models were changed to accommodate data in the form of krg versus capillary number and the ratio krg/kro. Wetting behaviour and wetting transition of oils on water in the presence of gas A thorough understanding of the wetting behaviour of simple oils on water has been acquired. It has been demonstrated that the equilibrium wetting behaviour of oils on water in the presence of gas does not obey the conventional picture. It involves three, rather than two, different wetting states. Oils, at least those oils mostly composed of alkanes, display on water an intermediate wetting state between partial wetting (oil lenses) and complete wetting (thick oil film). This state, referred to as frustrated-complete wetting, consists of oil lenses coexisting at the surface of water with a mesoscopic (i.e., several tens of molecules, or around 100Å -thick) oil film. The location of the different wetting states can be predicted as a function of oil composition (alkane chain length), brine salinity, temperature and pressure. This understanding arises primarily from ellipsometry measurements of equilibrium oil film thicknesses. The study of the effect of surface active agents (impurities, asphaltenes) on the wetting behaviour has showed that presence of surfactant changes the equilibrium wetting state of partial wetting into the frustrated-complete wetting state. Crossover EOS incorporating the singular behaviour near the critical point Equations of state are needed that account for the long-range fluctuations as occurring in the near-critical region of a fluid. In this work emphasis has been put on adjusting the Peng-Robinson equation of state accordingly. The Peng-Robinson equation is a cubic equation of state and it is widely used in industry, especially for refinery and reservoir simulation. This equation requires knowledge of the critical parameters and acentric factor and leads to good phase equilibrium predictions for hydrocarbons. But in the region near the critical point of a fluid, cubic equations are inherently inaccurate. A global crossover EOS was obtained that incorporates the singular behaviour near the critical point and classical behaviour far away from the critical point for pure fluids. The asymptotic behaviour satisfies universal scaling laws with universal critical exponents and universal amplitude ratios, which are very well established theoretically and experimentally. The shape of the top of the coexistence curve is repaired correctly and the "classical" critical point is shifted to its actual position. The value of the compressibility factor Zc of the crossover Peng-Robinson equation is equal to the experimental value. The crossover behaviour is controlled by only one non-universal system-dependent parameter related to the range of intermolecular forces. This parameter can be found from experimental data. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
