Well flow rate surveillance is essential for reservoir characterization and selecting potential activities and optimization production. Ideally, surveillance would be achieved using multiphase meters on each well, but generally it is not economically feasible especially for subsea production system. Therefore, the technology of virtual flow metering comes up.
In this paper, the development and application of virtual flow metering system, used for determining production rates including gas oil and water flowrates in well, is discussed. Without any metering devices, the system, developed by China University of Petroleum, can automatically estimate single well and whole production rates every five minutes, only taking advantages of the instrumentations typically installed on wells. In hardware, the system is mainly made up of two servers, one of which in charge of communication, the other calculation. In software, the core algorithms are based on validated models of well hydraulics and flow through choke in oil industry. Also, the components and heat transfer influence is also taken into considered by their corresponding models. Based on these models, three independent algorithms are established for well flow rates prediction. Each algorithm is replicable for others in order to prevent measurement distortion and end caused by individual instruments faults. The value of estimated flow rate uncertainties in addition to real-time continuous well flowrate estimates is described. The flowrate basis on a daily or weekly reconciled by real-time calibration program basing on calculated uncertainties.
The system practically applied in one subsea production system producing gas-condensate. In field commissioning, the system showed a great accuracy. The total mass flow rate and volumetric flowrates for each phase at standard conditions calculated with VMS showed a great agreement with the field data. The maximum error is below 10% and the averaged error is nearly 5%.