Design and Validation of a Numerical Model for Inclined Oil-Water Flow

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The proposed research seeks to develop and validate a time dependent, 3D numerical model of inclined oil-water pipe flow. Inclined oil-water flows are commonly encountered downhole in oil wells at depths where the hydrostatic pressure is too high to allow dissolved gases to come out of solution. 'Production Logging Tools' (PLTs) are used by oil companies to make fluid flow measurements in such oil wells, as part of the process of maximising oil production from UK reservoirs, and the numerical model will greatly facilitate interpretation of measurement data from these PLTs. Inclined oil-water flows are highly complex due to the presence of Kelvin-Helmholtz (K-H) waves which intermittently form and decay. The effect of these waves is to induce large, time dependent variations in the magnitude and direction of the local velocity vector of both the oil and water as well as causing large time dependent variations in the local volume fraction distribution of both phases. It is intended that the numerical model will predict the fine detail of the structure of inclined oil-water flows including (i) time dependent variations in the local velocity vector distribution of both phases; (ii) time dependent variations in the local volume fraction distribution of both phases; and (iii) the structure and propagation speed of intermittent K-H waves in the flow. If the model is successful in predicting the propagation speed of K-H waves for a wide range of flow conditions this will greatly facilitate interpretation of a novel Production Logging technique which estimates the oil-water mixture superficial velocity from measurements of the K-H wave speed. The numerical model will be validated in oil-in-water flows using a laboratory flow loop and two independent, state of the art measurement techniques which enable time dependent measurements of the local velocity vector of the dispersed phase (oil) and the local volume fraction of both phases to be measured. These techniques are; (i) high speed dual-plane Electrical Impedance Tomography (EIT) and (ii) the local, multi-sensor conductance probe. Both techniques can operate at high values of the mean dispersed phase volume fraction (e.g. for oil-in-water flows EIT operates up to about 45% oil volume fraction and the local probe operates up to about 30% oil volume fraction) where optical techniques such as PIV and LDA cannot generally be used due to the effects of light scattering from multiple oil droplet surfaces and the opacity of the oil-water mixture. Given the highly novel and innovative nature of both high speed, dual-plane EIT and the local multi-sensor conductance probe, work will be undertaken to develop these techniques such that measurements obtained from them are of sufficient accuracy to be useful in validating the numerical model. Since both measurement techniques are novel, an important feature of the proposed research will be the cross-checking of these techniques against each other.