TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWhen oil is produced under high water-cut conditions, oil in water emulsions can be formed. The break-up of oil droplets predominantly takes place in the choke valve. We have conducted laboratory experiments to investigate the effect of flow through a choke valve on the oil-droplet-size distribution in the emulsion. In these experiments the choke is modeled as a circular orifice in a pipe. The droplet sizes after break-up can be correlated to the mean energy dissipation rate per unit mass in the orifice. The experiments have been conducted with two set-ups on a different scale. The relation, which we have derived for the maximum stable droplet diameter downstream of the orifice can be applied to both scales. Furthermore the effect of oil viscosity on the droplet sizes after break-up has been investigated.

Is paper WS selected for presentation by an SPE Program committee following review of information cnntained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been revtewed by the S@ety of Petroleum Englneera and are subject to mrretion by the author(s). The material, as presented, does not neceaearlly reflect anỹ ition of the society of Petroleum Engineers, ita ofricera, w members. Papers presented at SPE meetings are subject to pubK@tion retiew by Editorial Committees of the Scdety of Petroleum Englneara. Electronic reproduction, distribution, or storage of any part of this paper for mmmerdal pu~ee tithwt the written mnsent of the Sdety of Petroleum Engineers Is prohibited. Permission to raproduce In print is restricted to an absbad of not more than 300 wurds; illustrations may not be mpied.The abstrad must mntsln wnsplcuous atiowledgment of Mere and by whom the paper was preeented. Write Librartan, SPE, P.O. Mx 833636, Ritiardson, TX 7S0S3-3836, U.SA., fax 01 -972-952-%3S. AbstractFor oil production under high water cut conditions the efforts needed for de-oiling of the production water are mainly determined by the oil-droplet-size distribution of this water. This distribution is predominantly the result of droplet breakup in the choke valve. To determine the effect of the choke valve on the droplet-size distribution, we have conducted laboratory experiments in which we used a circular orifice in a circular pipe. With the help of theory on droplet break-up in turbulent flow and with knowledge of the flow field inside an orifice, a prediction of the distribution after break-up can be made. It is shown that the droplets increase in size with increasing oil viscosity and Mermore it appears that, for the description of the break-up process, the distribution of the turbulence over the orifice zone is an important factor.

This paper was presented as part of the student paper contest associated with the European Petroleum Conference. Abstract Production of a well at high water cut is associated with problems in separation efficiency of the oil-in-water emulsion. In this, the smallest sizes of the oil droplets are the decisive factor, negatively and greatly influenced by the choke valve. This valve breaks the produced distribution down to too many and too small droplets for the separation equipment to economically clean the water and isolate the oil. Laboratory experiments allowed us to investigate the break-up effects of choke valves and to validate existing predictive theories. By using different choke types, significant reduction of break-up was accomplished. The effect of choke geometry on break-up is explained by an interplay of the time that droplets remain in a choke on the one hand, and the time needed for complete break-up under the current turbulence regime on the other. Hereby, the spatial distribution of energy dissipation, linked to the geometry of the choke, plays an important role. Introduction Often water is produced along with oil. When the age of a well matures, the water cut tends to increase. In the after-life of a well, the percentage of water can by far exceed that of oil. Wells with water cuts of 95% are no exception, which implies that these wells produce an oil-in-water emulsion. Chokes are installed on every well to control the pressure and flow rate. They work on the basis of energy dissipation by increased turbulence. Downstream of the valve the pressure is brought down to safer values to work with, and the emulsified liquids must be separated. This should be done carefully in order not to loose valuable oil and to clean the water before disposal. The efficiency of a separator is confined by the droplet-size distribution offered to it.