Enhancing Offshore Production Allocation with Virtual Flow Metering: A Comprehensive Methodology

This paper details the development and implementation of a Virtual Flow Metering (VFM) methodology for accurate allocation in an offshore field. Some wells can be individually aligned to the test separator, while others can only be aligned in commingle. The VFM system is a real-time, computer-based method for well rate determination, utilizing well flow models combined with sensor and instrumentation data for continuous multiphase flowrate estimation. The VFM methodology adheres to API MPMS 20.5 standards. It integrates laboratory analyses (PVT, chromatography, BSW%, viscosity) with real-time pressure and temperature data to estimate multiphase flow rates. The workflow involves calibrating well flow models using data from pressure and temperature sensors along the production path and aligning production with test separators for wells where individual alignment is possible. For wells that can only be aligned in commingle, production rates are measured using multiphase flow meters (MPFM) and estimated using the same VFM methodology. The VFM workflow includes the following key steps: Data Collection: Real-time data from offshore sensors and laboratory data are stored in an onshore historian and used as input for the integrated model. Model Integration: The integrated model combines PVT, well, subsea lines, and topsides oil path data to estimate flowrates with high accuracy. Rate Estimation: Three methods are used for flowrate estimation: well performance models, surface network models, and choke models. These methods are cross-checked to ensure redundancy and reliability. Rate Allocation: Production rates are allocated using well test figures and validated against fiscal metering on topside. The integrated production model ensures accurate daily production allocation and continuous optimization. The VFM system has been tested for 23 months, demonstrating a match error lower than 3% per well alignment and less than 1% for The total field oil rate compared with fiscal flowmeter data. The system effectively identifies daily production changes, tracks well performance, and provides alerts for corrective actions. The integrated model calibration process ensures accurate well performance and subsea line calibration, resulting in reliable production estimates. The VFM system enhances the petroleum industry's knowledge by providing a reliable, real-time solution for well rate determination. It improves data redundancy, serves as a backup for existing meters, and calculates flow rates without direct measurement. Continuous model updates based on well tests and lab data optimize well and surface network systems, especially in offshore fields where continuous well test alignment is challenging, thus advancing production data accuracy and reliability.