Computational Method to Assess Concentration of Water in Crude Oil Downstream of a Mixing Section

Abstract

This paper describes a method for predicting the concentration distribution of water in crude oil in a pipe section downstream of a region of mixing and droplet break-up.

The complexity of the problem and the necessary simplifications are described. The method with its approximations is justified on grounds of possible savings in financial outlay.

Details of governing equations, computational method and boundary conditions lead on to the link between forces on the droplet and the velocity of the droplet relative to the bulk liquid. The model incorporates turbulence enhancement and decay, and secondary velocities likely to approximate to those following a T-piece or bend or swirl-creating element.

The computer program was tested against data provided by BP and the results suggest that if the predictions indicate adequate mixing then they are likely to underestimate the uniformity of the mixture.

The predictions may be used to assess the suitability for sampling based on Case 1 of the draft ISO Standard (1) but must not be used to assess the suitability for sampling based on Case 2 of the draft standard unless fall-out has been allowed for in the program.

The paper reviews the assumptions and approximations involved in this model. Further work in these areas is needed to allow the model to be used with greater confidence.

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