Study On Oil Volume Fraction Measurement Based On Coriolis Flowmeter And Coaxial Conductance Sensor

Oil-water two-phase flow is widely present in the exploitation and transport of crude oil. Oil volume fraction is a significant parameter in the oil-water two-phase flow measurement. The oil holdup was measured by the Coriolis mass flowmeter and the coaxial conductivity sensor in this paper. Besides, the relationship between the real oil volume fraction and the oil holdup measured was investigated. The main contributions of this paper are shown as followed:1. The oil holdup of the oil-water two-phase flow was experimentally measured using Coriolis mass flowmeter. The ratio between the real oil volume fraction and the oil holdup measured exhibited a reverse U-shape characteristic with the increase of oil volume fraction, which increases at first and then decreases. Due to the complex geometry of the U tube, it was impossible to theoretically analyze this phenomenon in the Coriolis mass flowmeter. However, based on the flow dynamic of the oil-water two-phase flow and the principle of Coriolis mass flowmeter, 3D Computational Fluid Dynamics (CFD) of the U-shaped Coriolis mass flowmeter was carried out. The results from 3D CFD showed similar trend with the experimental results, which proves that the reverse U-shape between the oil volume fraction and the oil holdup is the intrinsic characteristic of the U tube Coriolis mass flowmeter.2. Based on the investigation on the geometry of the conductivity sensor used now, a coaxial conductivity sensor with guard electrodes and the corresponding measurement system were designed. Besides, the geometry of the conductivity sensor was optimized. The coaxial conductivity sensor was manufactured as optimized. In order to verify the applicability of the coaxial sensor, a series of oil-water two-phase flow tests was conducted in vertical upward and downward pipes on the multiphase flow test rig at Tianjin University. The measurement results of the coaxial conductivity sensor were used to calculate the oil volume fraction using different models. When the oil volume fraction was lower than 50%, the minimum error between the oil holdup measured and the real oil volume fraction could be obtained by the Maxwell model, which is within 2%. When the oil volume fraction was between 50% and 70%, best performance can be gotten using the mean value between the Maxwell model and Brrugenman model, the error of which is within 6%. The relationship between the oil holdup and the oil volume fraction of the oil-water two-phase flow was investigated using the vertical installed coaxial conductivity sensor. A trend happened both in the vertical upward and downward flow: with the increase of the oil volume fraction, the ratio between the real oil volume fraction and the oil holdup measured changed from larger than 1 to smaller than 1. This rule is caused by the oil-water distribution in the vertical pipe. It is an inherent phenomenon when measuring the oil volume fraction and the oil holdup in the vertical pipe.