Abstract

Flow-rate testing is the most fundamental and essential form of reservoir surveillance and is typically performed on a monthly basis using a test separator. This case study reviews the results from modelling a well located in a jungle for which poor testing quality precluded inflow analysis. The main causes were logistical difficulties, large flow transients, and phase segregation in the flowline between the wellhead and test separator.

A virtual flowmetering technique was investigated to determine a trend of reservoir pressure and skin and identify production optimisation opportunities. The algorithms used real-time data from permanent downhole gauges and electric submersible pump (ESP) surface controllers, which provided the necessary measurement frequency, resolution, and repeatability to capture well performance transients and provide a full production history. The liquid rate calculation used the principle that the power absorbed by the pump is equal to that generated by the motor. Water cut was calculated by modelling the production tubing pressure drop with a multiphase correlation.

Virtual flowmetering is demonstrated to provide a credible alternative where test separators and multiphase meters cannot be deployed owing to logistical difficulties such as in swampy terrain or on unmanned platforms and subsea. Furthermore, the high frequency, resolution, and repeatability of this particular flowmetering technique are greater than those obtained with traditional monthly, or even weekly, test separator data. This case study illustrates how these three attributes enhance nodal analysis, pressure transient analysis (PTA), and superposition, which enabled monitoring the well's reservoir pressure and well interference without the need to conduct pressure buildups.

Additional value comes from extending the application of this virtual flowmetering technique to wells that do not have testing difficulties, especially those that are under producing and require detailed diagnostics (e.g., PTA). The technique is also well suited to application in true real time because it is analytical, valid across the full pump range, and able to capture transients without requiring an iterative process. Is real-time flow rate just around the corner?

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