A case study is presented on increasing operational efficiencies using fiber optic-equipped coiled tubing to perform distributed temperature sensing (DTS) and distributed acoustic sensing (DAS) in conjunction with millout operations. In unconventionals with plug-and-perf or sliding-sleeve completions, hydraulic workover or coiled tubing is deployed to millout and clean the wellbore to total depth (TD) before the well can be put on production. Traditionally, the millout and cleanout process is a standalone operation. In the event a diagnostic service is performed on the well, a workover rig, coiled tubing unit, or wireline would be deployed in a second intervention after the initial millout is performed. This method presents a challenge to operators who want to bring wells online in a timely and economical manner.
By combining the millout and diagnostic cababilities into a single operation, operational efficiencies were significantly increased for the operator. Operators were able to minimize exposure to in-well operations and reduce the number of interventions necessary to bring a single well online. This resulted in a reduction of well shut-in time and faster data turnaround time on diagnostic evaluation. Simultaneous milling and diagnostic services were completed on 31 wells throughout 2018. Plug/Sleeve/Sand millouts were performed to well TD with a fiber-optic capable coil-tubing unit. Then the same work string was used to gather diagnostic data on the entire completion interval during the same run. These diagnostic data were collected and provided to the operator in an effort to better understand the completion design and hydraulic fracture placement. The operational efficiency gained by deploying diagnostic services in conjunction with the millout services lowered the operator's operation costs by USD 100,000 and operations time by 36 hr on average.