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Artificial Lift Techbook 2016

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ARTIFICIAL LIFT TECHBOOK: CASE STUDY | May 2016 | 33 2011, the frst breakthrough Where the well cannot be tested by conven- tional means or a reliable production trend cannot be obtained, the operator can only resort to virtual fowmeters, which use exist- ing downhole and surface instrumentation to estimate fow rates in real time based on physical models, correlations or neural net- works. Schlumberger's Lift IQ real-time pro- duction fow-rate analysis service is one such proprietary virtual flowmeter specifically developed for electric submersible pump (ESP) wells. The algorithm uses real-time gauge data, which provide the necessary mea- surement frequency, resolution and repeat- ability to capture transients. The liquid rate calculation is based on the principle that the power absorbed by the pump is equal to that generated by the motor, which provides an equation that can be resolved for rate. Analytical equations are used through- out the process ensuring that physics are respected at all times, which yields greater confdence than analogous methods based on correlations and artifcial intelligence. Two key features of the liquid rate calcu- lation are: • The liquid rate calculation is indepen- dent of changes in water cut and gas-oil ratio (GOR), which is valuable as they are both diffcult to measure and vary with time. In actual fact, the energy conservation principle takes into con- sideration the changes in fuid properties, as they are implicit in the equations, although not explicit and therefore not required as inputs. • A single calibration is valid for long periods of time of up to four years in time as demon - strated during the 2011 feld trials. Most other virtual fowmeters used within the indus- try require recalibration every time there is a signifcant change in water cut and/or GOR, which defeats the purpose for most applica- tions. The single calibration feature is essential to using the fow-rate calculation algorithm in predictive mode. These features were key to enabling the automa- tion of the real-time production fow-rate analysis service and spurred Schlumberger to develop a true real-time liquid rate and water cut calculation pro- cess as opposed to post processing gauge data. The Lift IQ engine is located in the Cloud and can be accessed by any well that is connected to the Internet. 2015, the second breakthrough Even though only a single calibration is required over long production intervals, the real-time fow- rate calculation algorithm had two potential weak- nesses up to 2015. FIGURE 1. An example of the new Schlumberger PHI shows an excellent match. (Data courtesy of Schlumberger) Pump differential pressure/power psi/HP Pump differential power, psi PHI Pump Health Indicator Actual measurements from real-time data Measurements showing imminent failure Reference curve from factory test

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