Extending Salinity Operating Range and Water Detection Lower Limit of Multiphase Flowmeters

Abstract

With 20 years of operations, multiphase flowmeters (MPFMs) using a combination of venturi and multi-energy gamma-ray absorption have gained acceptance in the oil and gas industry by demonstrating reliable measurement and operational robustness. Nonetheless, some challenging operating scenarios are encountered such as significant water salinity changes in multiphase and wet-gas flows and rapid detection of small water quantities during production. Although MPFMs are not affected by small water salinity changes, inaccurate flow rates can be calculated when water salinity significantly departs from the initial properties. To maintain measurement metrology as per specifications, the water-point should be manually modified to track variations; however, this operation is time consuming and may incur nonproductive time. The salinity change measured by a newly developed sensor can be provided seamlessly to MPFMs to automatically update the water point calibration, thus ensuring good flow rate measurement performance over a wider water salinity range. Extensive validations at several flow loop facilities and field tests, including frac flowback operations, demonstrate the robustness of the method in terms of hardware reliability and the delivery of high-quality data when used with MPFMs with digital connectivity, which opens the way to unmanned production monitoring operations. Interpreting multiphase mixture's dielectric constant and electrical conductivity simultaneously measured by the new microwave water salinity sensor at a high data acquisition rate shows that water salinity can be tracked online in the presence of oil, gas, and sand, and small water quantities down to 50 ppm (part-per-million) water volume fraction (WVF), from the typical ~1000-ppm WVF for the MPFM, can be detected rapidly in multiphase and wet-gas flows. This paper describes the working principles of the new sensor that enable additional capabilities to maintain accurate water-liquid ratio (WLR) measurement in situations where significant water salinity changes occur and to provide a rapid, much lower WVF detection level. Successful cases demonstrating an accurate real-time salinity monitoring in flow loop tests and in field operations are also presented.

Microwave probe sensing location for Venturi-based real-time multiphase flowmeter

“…111027, 2022;DOI: 10.1016DOI: 10. /j.petrol.2022 3 over time through salinity measurement (Fiore et al, 2020). While flow sampling can be used to measure salinity, in certain circumstances, sampling may fail to track rapid changes in the salinity of produced water, due to, for example, sharp salinity gradient in the formation (McCoy et al, 1997) or water injection during enhanced oil recovery (Johansen & Jackson, 2000).…”

“…Hence, the electrical conductivity and dielectric permittivity of the fluid mixture in contact with the sensor can be inferred from the amplitude-attenuation and phase-shift of the reflected signal relative to the incident signal. Due to the sharp contrast of the permittivity and conductivity of water relative to oil and gas hydrocarbons, the WLR can be interpreted from the measured mixture permittivity and mixture conductivity (Fiore et al, 2020). Salinity can be obtained from the ratio of the mixture conductivity to the mixture permittivity at a given fluid temperature (Xie et al, 2004).…”

“…Salinity can be obtained from the ratio of the mixture conductivity to the mixture permittivity at a given fluid temperature (Xie et al, 2004). DOI: 10.1016/j.petrol.2022.111027 4 (Fiore et al, 2020) Currently, the microwave sensor is installed in the lower area of a horizontal blind-tee spool upstream of a vertically mounted Venturi-based MPFM for salinity measurement (Xie et al, 2013;Fiore et al, 2020). Even though the local flow in the lower area of the horizontal blind-tee is liquid-rich, it is desirable to make the flowmeter installation more compact by integrating the microwave sensor with the vertically mounted MPFM.…”

“…1. Schematic diagram of open-ended coaxial microwave sensor and signal interpretation(Fiore et al, 2020)…”