Field Tests Evaluate Nonradioactive Multiphase Flowmeters

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 229654, “Field Evaluation of Nonradioactive Multiphase Flowmeters: Performance Comparison, Accuracy, and Reliability Assessment, ” by Ruwayshid Almurayshid, SPE, Hamoud R. Alshammari, SPE, and Eldar Sadikhzada, Saudi Aramco, et al. The paper has not been peer-reviewed. _ Non-nuclear multiphase flowmeters (MPFMs) offer an alternative to traditional nuclear-based flow-metering systems, addressing environmental and regulatory concerns while potentially maintaining measurement accuracy and reliability. The objective of this study was to field test a non-nuclear MPFM and assess its performance under challenging operating conditions. The non-nuclear MPFM demonstrated reliable performance in measuring multiphase flow rates of oil, water, and gas during flowback operations, with measurement accuracy within an acceptable margin of error compared with conventional separator data, with good repeatability under varying flow conditions. Non-Nuclear Multiphase-Flow Measurement The MPFM deployed in this study offers full-range, non-nuclear capabilities with enhanced data intelligence and operational simplicity. This technology is engineered for versatile production environments, including heavy-oil and wet-gas applications, and monitors individual or group wells accurately in real time. By eliminating the necessity for costly test separators and circumventing complex nuclear-source management, this system reduces both capital and operating expenses significantly while improving well-test frequency and data accuracy concurrently. The system’s core design integrates three distinct but complementary technologies: sonar, near-infrared (NIR), and a Venturi meter, alongside an intelligent flow computer. This multisensor approach enables precise characterization of multiphase flow across a broad spectrum of gas/liquid ratios without requiring external separation or a gamma densitometer. System Components and Measurement Principles Sonar Technology. Produced fluids generate self-sustaining turbulent eddies that propagate along the pipe. An array of axially distributed pressure sensors measures precisely the dynamic pressure fluctuations associated with these eddies. Phased-array processing algorithms analyze these patterns to calculate the bulk flow velocity. This bulk volumetric flow rate is directly proportional to the convective velocity measured by sonar. In wet-gas configurations, sonar serves as the primary total-flow-rate measurement. Within a multiphase-flow context, it functions as the total-flow-rate measurement at high flow rates and provides a crucial cross-check for the Venturi nozzle at normal operating conditions. Additionally, an array of external strain sensors contributes data for gas, liquid, and mixed phases, which is processed by a proprietary algorithm requiring no recalibration. NIR. The NIR sensor provides full-range water-cut measurement. This sensor operates independently of brine salinity and liquid-density variations, and is, notably, insensitive to entrained gas. The meter is founded on the principle of NIR absorption. Oil and water possess distinct absorption spectra in the NIR region. By meticulously measuring light absorption at key wavelengths, the meter quantifies the relative concentrations of oil and water accurately, irrespective of free gas content. This absorption measurement targets the molecular structure of water and oil, rather than dissolved components such as salt, ensuring robust accuracy regardless of water chemistry. Venturi Meter. The Venturi meter, a differential-pressure device, provides a measurement directly related to the flow momentum of the multiphase mixture. This enables the determination of either fluid density or volumetric flow rate. In scenarios where an independent measurement of volumetric flow rate is available, the Venturi can output the mixture density by applying the momentum balance, assuming homogeneous flow within the nozzle. A linear dependency between the fluid-mixture density and the gas volume fraction (GVF) can be established. In the wet-gas configuration, the Venturi nozzle is used to measure GVF, whereas in the multiphase configuration, it serves as a primary input for total-flow-rate determination.