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. Interpreting the multiphase mixture's dielectric constant and electrical conductivity simultaneously measured by a 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 can be detected rapidly in multiphase and wet-gas flows.

The detection of the first produced water is of paramount importance in many applications, such as for fields with high H2S production, where existing processing plants usually have limitations in treating produced water with dissolved H2S. Early detection of produced water in oil is required, enabling operators to take informed decisions about the oil production strategy as well as water treatment and corrosion protection plans. Extensive analyses in flow loops and field operations with the new microwave water salinity sensor demonstrate that the water detection limit is lowered from the typical ∼1000-ppm water volume fraction (WVF) for the MPFM to a remarkably low 50 ppm.

This paper describes the working principles of a new sensor and method, 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 first-water detection in flow loop tests and in field operations are also presented.

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