Completion Integrity Evaluation by Distributed Acoustic and Temperature Sensing Data Acquisition Through Coiled Tubing Real-Time Telemetry System

An intensive well integrity (WI) examination was carried out utilizing distributed acoustic sensing (DAS) and distributed temperature sensing (DTS) tools through coiled tubing (CT) with real-time telemetry system in a horizontal gas well completed with open hole (OH) multi-stage fracturing (MSF) completion. During well completion, an unexpected leak in the lower completion led the OH packers not to effectively set. The WI examination was needed to locate the leak and effectively salvage the well. With DAS and DTS systems connected to the optical-fiber cable through the CT pressure bulk head at surface, CT conveying a bottom hole assembly consisting of conventional noise logging tool, temperature and pressure sensors, gamma ray and casing collar locator was run in the wellbore to the toe depth. The DAS and DTS data were recorded under shut-in, flowing and injection conditions keeping the CT stationed near to the toe depth. After recording DAS and DTS data in each shut-in, flowing and injection modes, noise logging was also performed by moving the CT across the entire horizontal section. The DAS optical interrogator unit connected, at surface, to optical-fiber cable deployed in the well successfully measured the Rayleigh backscattered light to provide a local measurement of the dynamic strain, which was converted into seismic wave fronts. The purpose of running noise logging tool was to validate acoustic wave fronts and interpretation obtained from the DAS and DTS. This comprehensive investigation involving DAS and DTS allowed to detect acoustic events simultaneously at multiple points along the entire wellbore through its capacity of providing the fluid movement visualization and detection: into or out of reservoir and evaluation of flow behind pipe and OH packers. DAS and DTS have also proved to be quick and operationally efficient techniques that can be done with minimum number of trips to surface and without complex bottom hole assembly. DAS system provided an opportunity for seismic data acquisition, where it significantly improved the efficiency of wellbore integrity diagnostic operations. A full well profile was recorded for each scenario in only minutes, rather than hours for a conventional tool survey. This paper elaborates facts on DAS data acquisition and how first time DAS data acquisition led to create a difference as comparison to the use of conventional CT.