Emulsion flow in porous media and its application in alkaline flooding for heavy oil reservoirs.

摘要

Emulsion flow in porous media has been extensively studied but, as yet, is not well defined or understood. Emulsion viscosity is found to be one of the flow rheological properties which can be used to characterize emulsion flow in porous media. Numerous efforts have been made to determine the viscosity of oil-in-water (O/W) emulsion in porous media; whereas few attempts have been made to quantify the viscosity of water-in-oil (W/O) emulsion. Almost two thirds of crude oil worldwide is produced in the form of W/O emulsion. The aim of this research is to experimentally determine the viscosity of W/O emulsion in porous media and theoretically model the emulsification processes for alkaline flooding in heavy oil reservoirs.;Techniques have also been developed to experimentally and numerically determine the increase in pressure drop and oil recovery associated with alkaline flooding for heavy oil reservoirs. Experimentally, pressure drop and oil recovery have been measured for enhancing heavy oil recovery during the alkaline flooding processes. It has been found that both pressure drop and oil recovery are increased as alkaline concentration is increased. The increase in pressure drop is due mainly to in-situ formation of water-in-oil (W/O) emulsions and thus, oil recovery is improved because of blockage of the high permeability zones induced by the preceding waterflooding. Theoretically, a simulation technique has been developed to model and match the experimental measurements for the alkaline flooding processes. An excellent agreement between the measured and simulated pressure drop and cumulative oil production are obtained by taking both the measured viscosity of W/O emulsions and the relative permeability into account. The displacement mechanisms of alkaline flooding in heavy oil reservoirs (i.e., in-situ generation of W/O emulsion) have been numerically simulated and matched. In particular, it is numerically found that the W/O emulsion is in-situ generated in the high permeability zones. This finding is consistent with the experimentally determined displacement mechanisms (i.e., in-situ generation of W/O emulsion) in the literature. Both the experimental findings and the newly developed simulation technique will facilitate simulating and designing field-scale alkaline flooding for heavy oil reservoirs.;Experiments have been conducted to determine the viscosity of W/O emulsion in porous media. W/O emulsion is first prepared for different volume fractions of the dispersed phase and then characterized for its properties and rheological parameters including flow index and consistency constant. All the prepared W/O emulsions with a volume fraction between 6.78% and 33.48% are found to behave as non-Newtonian shear-thinning fluid with a fairly high viscosity. Subsequently, the viscosity of W/O emulsion is measured during the emulsion flow in three types of sandpacks. Correlations of the viscosity of W/O emulsion in porous media have been developed by performing a regression on the experimentally measured data. The newly developed correlations are validated, while sensitivity analysis is performed to examine tortuosity and emulsion quality effects. The existing correlations for O/W emulsions provide underestimated predictions for the viscosity of W/O emulsions, while the droplet size distribution does not impose a significant impact on the viscosity of W/O emulsions tested in this study.