Inverted Venturi: Optimising Recovery Through Flow Measurement

Abstract The advent of high crude oil prices and mature fields has seen a rush for efficient recovery methods. This has spurred the development of "monitor-feedback-control" systems through intelligent well system (IWS) and interventional processes. Traditionally, downhole permanent flow measurement is performed using differential pressure meters; e.g. venturi. The intrusive nature of these flowmeters prevents easy access for interventional processes and creates a loss in well lift. The main aim of an inverted venturi design is to allow full bore access whilst maintaining the downhole measurement accuracy requirements. The flowmeter has a reverse mechanical design compared to a restrictive venturi. Instead of a constricted section in the tubing, the inverted venturi has an expanded section. The theoretical principles are still based around simple energy and momentum conservation. Due to these facts, the operation of the tool requires the use of a pair of high resolution pressure gauge. The main breakthrough came from the development of a high resolution pressure transducer. Surface testing of the flowmeter has demonstrated flow measurement uncertainty better than 8% for instantaneous flow rate measurement and better than 1.5% in bulk flow rate measurement. These flowmeters have also been deployed successfully in the field. Installation of these flowmeters in the Gulf of Mexico (GOM) region has shown a similar level of accuracies and has provided immense value to production. Apart from providing full bore access, the flowmeter is more robust as it is able to withstand higher gas volume presence in production rather than that of restrictive venturi. Due to the sensitivity of the pressure transducer, the flowmeter is also able to detect the presence of gas in production which adds value to the recovery process. Installations are planned in the near future in IWS applications. These will include applications for multi-zone allocation flowmeters, injection flowmeters for both gas and water applications and commingled flow production meters. The application for the inverted venturi is limitless as it is not constrained by the typically issues surrounding restrictive venturi such as the loss of wellbore access and well lift.