The Causes Of The Transformation Of O/W Emulsion And Its Countermeasures

The technology of emulsion viscosity reduction (O/W) has been more and more widely used in oilfield both at home and abroad, which has achieved good results and benefits. However, sometimes the viscosity of the transformation emulsion (W/O) increases dramatically which seriously affects the emulsion viscosity reduction effect. Therefore it brings a lot of difficulties in the production and transmission. In this paper, various influence factors of O/W emulsion in the transition were researched in the lab. First, the characters of crude oil were studied. Experiments showed that resin and asphaltene promoted the transformation of O/W emulsion, and that the asphaltene was a bigger impact than resin. Meanwhile aromatics played a certain extent in the transition of O/W emulsion of crude oil. Second, some factors related to the impact of the O/W emulsion in transition were researched, such as salinity, divalent ions, pH value and so on. It was showed that an appropriate salinity (1000~4000mg·L-1) and pH value (10.0~12.0) was suit to stabilize the O/W emulsion, while the addition of divalent ions promoted the transformation of O/W emulsion. Third, other factors related to the transition of O/W emulsion were studied, for instance, the ratio of oil-water, the transition temperature, polymers,surfactants and so on. It displayed that the flow of the O/W emulsion is not easy to transition under the critical shear rate (8r s-1). With the temperature increasing, the stability of the O/W emulsion declined. And the type of surfactants played an inhibition role in the transformation of the O/W emulsion. A small amount of polymer was suit for the stability of the O/W emulsion. Fourth, the mechanism of the transformation of the O/W emulsion was analyzed. At last, the preventive measures were summarized, and also, the prevention systems were researched by changing the oil component, selecting the appropriate surfactant and changing the production conditions. At the same time, other prevention systems were researched according to different salinity waters and viscosity crude oils. Those systems could be applied to different fields of heavy oil with more than 98% viscosity reduction, which had the features of adaptable and not easy to transform.