This paper presents the development and validation of a tool for multiphase flow rate estimation, based on the choke valve geometry, the fluid characterisation and the process parameters upstream and downstream the choke, such as pressures and temperatures.
The tool is able to work on-line, with real-time data demonstrating a high flexibility in application on different wells and producing scenario. The tool is based on the HNE-DS methods and tunes automatically a set of coefficients in order to correct the estimated ideal flow rate into a reliable output. Starting from a known operating condition, it calculates the gas and liquid discharge coefficient with the Chisolm and Lenzing theories and estimates flow rates at other unknown operating conditions. The ω-model with Diener corrections has been verified and extended in order to include three-phase flow and the PVT analyses of the fluids.
The workflow has been developed with an efficient computational solution for real-time application. The tool has been validated against the readings of multiphase flow meters (MPFM) installed on several production wells operating in Western and North Africa. The results reported in the paper show a high level of efficiency and accuracy, completely comparable with MPFM and well test analysis. Furthermore, using the discharge coefficient predicted by Lenzing it is possible to decrease the value of the mean square error of the ω-model with Diener corrections, increasing the precision of the tool. It is important to highlight that the real discharge coefficients are highly dependent on valve discharge geometry.
Finally, it is important to highlight that well tests are still necessary and not replaceable by the prediction tool itself, but their schedule can be reviewed in order to maximize the wells production and availability while maintaining a high quality of field monitoring. The predicted flow rate has been used and applied not only for monitoring but also to tune reservoir, process and fluid-dynamic models that are used for field development, forecast production scenario, troubleshooting and production optimization purposes.
The business value of the work is represented by the possibility to check instrumental failure, remote production monitoring and optimization, quick back allocation and real-time multi-phase flow rate prediction for wells without instrumentations. The tool can be implemented as a digital oil field virtual metering application, introducing an innovative approach that uses simple available well data to compute multiphase flow rate.