Труды Института механики им. Р.Р. Мавлютова
Электронный научный журнал | Electronic Scientific Journal
Proceedings of the Mavlyutov Institute of Mechanics
The paper presents the results of hydrodynamic studies of inverse water hydrocarbon dispersions: emulsions and, prepared from it by freezing the dispersed phase, suspension. In addition to the high viscosity of the emulsion, a much higher viscosity of the carrier phase, the success of the use of invert emulsions in the oil industry is due to the dynamic blocking effect. The effect is that the flow velocity in the capillary structures and cracks decreases by 3-4 orders of magnitude, in spite of the constantly acting pressure drop. The work shows an increase in viscosity with decreasing temperature, while the degree of blocking of the emulsion is higher than that of the suspension prepared from it. The ultrasonic effect makes it possible to control the effect of dynamic blocking. The short-term effect of ultrasound makes it possible to restore the flow, while a longer exposure leads to the fact that blocking occurs even in ultrasound.
water hydrocarbon emulsion,
dynamic blocking effect,
The article deals with experimental studies of inverse water hydrocarbon dispersions: emulsions and prepared from it, by freezing the dispersed phase, suspension. A physical blocking mechanism associated with deformation of microdroplets of dispersed phase water is given in the paper. To study the features of the mechanism of display of this effect, experiments are performed with a change in the aggregate state of the dispersed phase (frost of water microdroplets) and in the influence of ultrasound.
The aim of the paper is to broaden the limits of the applicability of the dynamic blocking effect by solving the following problems:
1) To study the influence of deformation of droplets on the flow of an emulsion in the Hele-Shaw cell in the event of a blockage. The problem was solved by comparing the hydrodynamic features in the flow of the water-hydrocarbon emulsion and the suspension obtained from it by freezing the dispersed phase.
2) To study the effect of ultrasound influence (USI) on the flow of emulsion. The problem was solved by placing the Hele-Shaw cell with the emulsion into the ultrasonic bath and comparing the flow of the emulsion to the USI, at the USI and after the USI.
The experimental procedure consists of several methods of emulsion studies:
1) rheological studies of emulsions on a HAAKE MARS III viscometer;
2) hydrodynamic studies of the flow of the reverse water-hydrocarbon emulsion and the suspension prepared from it in a cylindrical microchannel; flow of the emulsion in the Hele-Shaw cell at different pressure drops with a short-term and constant USI.
The results of the studies show that the viscosity of the dispersion increases with decreasing temperature, but the degree of blocking of the emulsion is 1.5 orders of magnitude higher, this is due to the denser packing of microdroplets of water due to their deformation at significant pressure drops. The solid particles (icicles) of the suspension are slightly deformable, in contrast to the emulsion droplets, which allows the dispersion medium to be filtered through the structure of ice floes. Thus, the conclusion is again confirmed that the key role in the drop in the flow velocity with a constant pressure difference of 2 or more orders is played not so much by the viscosity of the dispersion as by the dynamic blocking effect, consisting in the deformation of water droplets, their ability to create a dense structure with no filtering through it, which can not create solid, non-deformable particles.
It was found that the action of ultrasonic fields with radially expanding flow almost completely restored the initial flow rate, but the time of blocking after turning off the sound transducer depended on the exposure time. With longer sound influence, the system gradually began to block, the change in the flow structure and the time of transition to the blocking state were approximately the same as initially, in the absence of ultrasonic fields. Thus, powerful ultrasonic fields can be used to control the effect of dynamic blocking, which is of great practical importance.