Measurement of Oil-Gas-Water Mixture Velocity Using a Conductance Cross-Correlation Flowmeter With Center Body in Small Pipe

To be able to acquire the mixture velocity of water continuous oil-gas-water three-phase flow in 20-mm inner diameter small pipe based on the cross-correlation method (CCM), accurate measurement of the cross-correlation velocity, and establishing valid relationship between cross-correlation velocity and mixture velocity is of importance. Due to the severe slippage effect and the non-uniform distribution of phases in three-phase flow, the correlation between the upstream and downstream signals is seriously affected, and the relationship between the cross-correlation velocity and the mixture velocity is extremely complicated. Moreover, the low-sampling frequency and noise also reduce the accuracy of cross-correlation velocity measurement. In this paper, a cross-correlation flowmeter (CCFM) with two ring-shape conductance sensors embedded on the center body is proposed. Based on the finite element method (FEM), the geometry of the CCFM is designed and optimized. A novel fast Fourier transform (FFT) interpolation algorithm is investigated to increase the sampling frequency while eliminating the noise. Afterward, the performances of the CCFM and the FFT interpolation algorithm combined with the CCM are experimentally evaluated. The results show that the CCFM can enhance the correlation of upstream and downstream signals while FFT interpolation algorithm can effectively increase the sampling frequency and eliminate the noise, which can improve the accuracy of cross-correlation velocity measurement. The CCFM also can simplify the relationship between the cross-correlation velocity and mixture velocity, and thus the mixture velocity can be satisfactorily predicted.