Production logging tools (PLTs) are used to evaluate downhole flow profiles under flowing and shut-in conditions before taking any well intervention decisions. Interpreting conventional centre- weighted production logging data is more complicated in deviated wells due to more complex flow behavior such as recirculation. Downflow of the heavy phase along the low side of the pipe occurs due to significant shear between the light and heavy phases, resulting in recirculation phenomena. A pipe centered conventional spinner tries to average the velocities of the phases passing through the swept area of the blades, but generally returns a velocity that is too low if not actually negative. A poorly centralized spinner often tends to indicate downflow due to the recirculation of the heavy phase. This paper shows how eccentered multi-spinner technology delivers accurate results for multiple phases in deviated wells where conventional spinners do not perform reliably.
An advanced PLT provides discrete velocity and hold-up measurements: five spinner velocity points and six pairs of water and gas hold-up points. This technology was initially designed for production logging in horizontal wells exhibiting stratified flow regime. It is also shown that multi-spinner measurements can be used to characterize recirculation behavior in deviated wells. To obtain quantitative fluid influx moving upwards, a new approach was used to calculate the average velocity without including the spinners immersed in recirculation zones. Individual phase hold-up was then calculated using a linear hold-up averaging technique from discrete hold-up measurements across the pipe interval.
Reliable results were obtained using this approach in deviated wells from both under shut-in and flowing conditions of low flow rate where a low mixture velocity and high slip velocity coexist. Recirculation poses serious problems when fluid velocity is low in the pipe. Typical example of this is PLT data acquired under shut-in condition. Generally, crossflow characteristic were missed in such wells and depleted zones cannot be identified. Two data sets acquired under flowing and shut-in conditions are discussed extensively. Downhole flow rate results were compared with surface flow rate measurement and an acceptable match was obtained between two rate measurements. In addition, the importance of selective performance analysis (SIP) was also shown.