Deploying Fibre Optics outside the casing
As part of CO2CRC’s Stage 3 Project, fibre optic cables were deployed to the outside of the casing. This provided some valuabel lessons for deployment. The Stage 3 Project team engaged with an industry leader in DAS systems to provide a tubing encapsulated fibre optics (TEF) suitable for downhole deployment which would be secured to the outside of the casing of each well, run through the injection interval and into the rathole section and incorporate an integrated turnaround immediately above the casing shoe. As the four monitoring wells were to be directionally drilled from two offset wellpads (two wells per pad), centralisation of the casing was critical to protect the TEF during deployment as well as to ensure the effectiveness of the cement to isolate the upper zones. An additional point of complexity associated with the installation, was the need to perforate the wells and establish reservoir communication for the purposes of pressure tomography. As the TEF was deployed through and below the target zone, the perforating charges had to be oriented away from the TEF to ensure they were not damaged.
The approach taken was to employ a 6spf gun down-loaded to 4spf such that a 180o phasing was left blank which would then be oriented toward the TEF. This directionality was ensured through the installation of a heavy duty blast protector (designed by project participant, InGauge Energy) which had the dual benefit to protect the fibres from the shock of the adjacent perforating event as well as having sufficient magnetic detectability that it could be identified by a conventional wireline logging tool. Importantly, the positioning of this device had to be aligned with the identification of the target zone for perforating and this was required in advance of running the casing section to which the device was attached. Consequently, a rapid open-hole log evaluation and perforation interval decision workflow was required to facilitate this decision process.
This approach proved to be successful with all wells perforated without damage to the TEF. The downloading of the perforating gun to avoid the TEF resulting in a reduced shot density across the target interval, however, will have certainly reduced the potential area open to flow of the perforated interval.
The system was commissioned and tested between March and June 2020. High quality seismic data has been acquired continuously from all wells on site outfitted with the TEF, since that time with excellent reliability and repeatability