In downhole dehydration the produced fluids – oil and water, with a low oil/water ratio – are separated at the bottom of the well by means of a hydrocyclone. In many cases this separation can be carried out successfully, because the size of the oil droplets is generally in such a range, that the hydrocyclone can remove the oil from the produced water. Potential problems are connected with the possible occurrence of very small oil droplets, because this may lead to the presence of some oil remaining in the produced water, which is unfavorable from an economical point of view and, moreover, which can lead to difficulties with subsurface injection of this water. Notably production from reservoirs with a relatively low permeability may lead to the presence of small oil droplets.

For conventional high water-cut oil production, the presence of very small oil droplets is predominantly caused by droplet break-up in the choke valve. Further downstream these small droplets determine the complexity of the separation units. It is shown that the geometry of the choke valve influences the break-up process. Consequently, by modification of the geometry of this valve it must be possible to reduce the break-up. It is expected that in this way a substantial droplet size increase can be realized.

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