Hydraulic modeling is a fundamental piece of any Managed Pressure Drilling operation using multiphase gasified drilling fluids. MPD Engineers rely on hydraulic flow modeling systems to predict equivalent circulating densities. Models also allow designing and manipulating hydraulic parameters such as gas/liquid ratios, pressures and flow rates to achieve desired conditions.

Therefore, the selection and calibration of the correct hydraulic model is critical for the success of any MPD Operation. The ECD calculation in an MPD operation is not the solely objective of using a complex modeling system. Today’s downhole drilling tools technology makes available a variety of sensors capable of measuring actual downhole pressure values. Prediction of flow behavior is also an important step that will increase the ability of monitoring and keeping efficient hole cleaning, cutting transport and heat transfer efficiency, which are critical for all multiphase drilling operations. Actual measurement of downhole equivalent circulating density becomes now a critical new calibration value to compare hydraulic models performance and approximation to reality.

This paper compares the two-phase hydraulic simulations results with the data gathered from a drillstring installed annular pressure sensor used while drilling a highly deviated well in a low pressure reservoir using nitrogen injection through concentric string technique in an MPD operation. This technique poses a series of new challenges for the MPD engineer that needs to predict hydraulic behavior created by the typical transient “U” tube effect caused by connections, trips and surveys in this kind of applications.

The paper details the model and calibration process, findings and best practices gathered from multiple runs, real time transmission and high definition memory data. Actual results and conclusions and also discussed and analyzed in depth for the benefit of any further concentric job applications associated with use of downhole pressure sensors.

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