Comparison of gamma densitometry and electrical capacitance measurements applied to hold-up prediction of oil–water flow patterns in horizontal and slightly inclined pipes

Abstract

Measurement techniques are vital for the control and operation of multiphase oil-water flow in pipes. The development of such techniques depends on laboratory experiments involving flow visualization, liquid fraction ('hold-up'), phase slip and pressure drop measurements. They provide valuable information by revealing the physics, spatial and temporal structures of complex multiphase flow phenomena.This paper presents the hold-up measurement of oil-water flow in pipelines using gamma densitometry and electrical capacitance tomography (ECT) sensors. The experiments were carried out with different pipe inclinations from −5° to +6° for selected mixture velocities (0.2-1.5 m s −1 ), and at selected watercuts (0.05-0.95). Mineral oil (Exxsol D60) and water were used as test fluids. Nine flow patterns were identified including a new pattern called stratified wavy and mixed interface flow. As a third direct method, visual observations and high-speed videos were used for the flow regime and interface identification.ECT and gamma densitometry hold-up measurements show similar trends for changes in pipeline inclinations. Changing the pipe inclination affected the flow mostly at lower mixture velocities and caused a change of flow patterns, allowing the highest change of hold-up. ECT hold-up measurements overpredict the gamma densitometry measurements at higher input water cuts and underpredict at intermediate water cuts. Gamma hold-up results showed good agreement with the literature results, having a maximum deviation of 6%, while it was as high as 22% for ECT in comparison to gamma densitometry.Uncertainty analysis of the measurement techniques was carried out with single-phase oil flow. This shows that the measurement error associated with gamma densitometry is approximately 3.2%, which includes 1.3% statistical error and 2.9% error identified as electromagnetically induced noise in electronics. Thus, gamma densitometry can predict hold-up with a higher accuracy in comparison to ECT when applied to oil-water systems at minimized electromagnetic noise.

Imaging irregular structures using electrical capacitance tomography

“…Electrical capacitance tomography (ECT) is a nonintrusive and noninvasive measurement technique, which can be used for the measurement of phase holdup in multiphase systems. ECT has been widely used in various applications, such as fluidised beds in the chemical, pharmaceutical and power industries [1,2], pipeline flows in the gas/oil industry [3,4], particle coating in the pharmaceutical industry [5,6], and in the medical field [7][8][9]. For some applications, it is necessary to deal with a high temperature environment [10] (e.g.…”

Horizontal annular flow through orifice studied by X-ray microtomography

“…gamma-ray densitometry (Hooker and Popper 1958). They are still frequently used today (Perera 2018). Further, radiographic techniques are also applied to 2D multiphase flow visualization and allow investigation of high-speed transient phenomena when using high-intensity synchrotron radiation (Karathanassis et al 2018).…”

Improving EIT-Based Visualizations of Two-Phase Flows Using an Eigenvalue Correlation Method

“…Moreover, EIT attracts special attention due to its low excitation amplitudes (of the order of mA or few V), making it safe and low cost. With these advantages, the EIT technique has been successfully applied to multiphase flow instrumentation [4], [5] and medical imaging [6].…”