Fiber-Optic Distributed Vibration Sensing Provides Technique for Detecting Sand Production

Abstract Throughout the past decade, fiber-optic technology has gained acceptance as a viable solution for continuous monitoring of distributed temperature profiles in a variety of downhole applications (Karaman 1996; Carnahan 1999). In wells completed with fiber-optic control lines, distributed temperature logs can be produced without well intervention. This paper reports a recent development of a surface instrument capable of measuring distributed vibration profiles on optical fiber. This technology has enabled an operator to identify downhole vibration events related to sand production. Applications for distributed downhole vibration sensing are extensive; the technology can be used to monitor and understand almost any process that generates a vibration signature. The frequency range of the fiber-optic sensor allows different sources of vibration to be discriminated. Therefore, the difference between the sound generated by multiphase flow noise and increased sand production is distinguishable with regard to frequency content. To assess the prototype system, several candidate wells with sand production issues were selected from the Deepwater Gunashli (DWG) field in Azerbaijan. These wells had been completed with openhole gravel packs and a fiber-optic sensing system installed outside the sand screens along the entire reservoir interval. On one of the wells, interpretation of the acquired distributed vibration data revealed the location at which the formation sand was penetrating the sand screens and migrating into the wellbore. Analysis of the distributed temperature data indicated that the location of the vibration spike signature corresponded to a high-producing interval. This paper outlines the principles of distributed vibration technology and how—for the first time in the industry—this technology was successfully used with fiber-optic distributed temperature sensing for downhole monitoring. The combination of these two systems enabled the operator to identify the sand entry depth and the corresponding sand-producing interval, eliminating the need for further high risk interventions.