Transferring Intelligent-Well-System Triple-Gauge Data Into Real-Time Flow Allocation
Authors: Sun Kai , Omole Oluwole , Saputelli Luigi , Gonzalez Fabio 
Published: November 2012

Knowing the exact flow allocation for each controlled zone is important for well optimization and the management of an intelligent well system (IWS). For two-zone IWS producers, a broadly accepted downhole gauge configuration uses the triple-gauge system, where two gauges give the upstream-side pressure/temperature (P/T) of the two downhole control valves and one gauge gives the P/T inside tubing of the commingled fluid [Baker Hughes IWS installation (2012) and Halliburton-WellDynamics IWS installation (2012) databases]. Theoretically, this configuration gives the P/T boundary conditions between the two valves and the gauge carrier, where flow allocations can be solved numerically, on the basis of the gauge readings and control-valve settings. However, from what we have seen in the past 10 years of IWS applications, only a few have published successful application cases regarding this topic. Is this an indication that a large number of two-zone triple-gauge IWS wells are operating in the low-confidence region of the two zone's production flow allocations?

In this work, a comprehensive hydraulic model has been developed to address this topic. This paper will discuss a recent application of such a model to estimate the flow allocations of an existing two-zone deepwater IWS oil producer. The well began production in 2007. A total of 1,362 daily triple-gauge data points are available for this study, where the monitored P/T data indicate that the well was flowed in multiphase conditions at downhole for a large percentage of its production life. Verification was completed by comparing the predicted flow-allocation results with this well's measured total rates and daily-allocation rates. Further comparisons of the zonal allocations, between the model calculated results vs. the zonal-reservoir deliverability-study predicted results, were also provided. These comparisons showed a good match between the predicted results, measured data, and the available reservoir-study results. Descriptions of key factors to address the accuracy of the method have been provided, including compensated differential pressure, multiphase choke model, choke-discharge coefficient, and fluid pressure/volume/temperature (PVT) behavior impact. Sun's modified multiphase choke model was proposed in this study. The authors believe it will be more suitable for downhole valve operating and multiphase-flow conditions.

This case study has proven a very promising independent solution for continuous well-rate estimation, with the solution based purely on choke-pressure drops and intelligent well-valve positions. The downhole monitoring P/T is normally based on seconds, which means that intelligent well-flow allocations can be calculated in real time without installing downhole venturi flowmeters that may add completion cost. In addition, a venturi flowmeter provides a smaller ID profile for the completion strings above/below it, which is inconvenient for future potential wellbore interventions. This solution brings measurable benefits for those IWS wells with no downhole flowmeters when taking into account the time and effort spent on periodic production tests, reservoir/well deliverability studies for production allocations, and potential production loss during the production tests.