Efficient Containment Monitoring with Distributed Acoustic Sensing: Feasibility Studies for the Former Peterhead CCS Project

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This paper investigates the technical feasibility of monitoring the Goldeneye storage site for containment with time-lapse Distributed Acoustic Sensing (DAS) VSP and DAS microseismic. Specifically, the study examines if the expected seismic signals are measurable with DAS, i.e. whether it would be possible to detect unintended migration of CO2 in a timely manner with sufficient resolution and spatial coverage. In the case of Goldeneye, the multiplicity of wells and diversity of their trajectories provide a favorable geometry that compensates for DAS broadside sensitivity limitations. A ray trace modelling exercise demonstrates that a multi-well DAS VSP survey with minimized source effort can provide a high fold image of the main storage site in an area of approximately 2 km2 around the platform and injectors. The feasibility of monitoring induced seismicity with DAS is evaluated in terms of the spatial distribution of minimum detectable moment magnitudes and event location errors. Provided the noise floor of DAS interrogation units will be reduced and given the Goldeneye well geometry, DAS microseismic may be a possible containment monitoring technology subject to field trial, noise characterization and further processing developments. The economics for DAS seismic solutions are advantageous given that a fiber optic cable can generally be cost-effectively installed in multiple wells and its use can be combined with other in-well monitoring applications, like Distributed Temperature Sensing (DTS). For the Goldeneye storage site, DAS VSP has been identified as a potential containment monitoring alternative to a much more costly surface seismic survey in the vicinity of the injector wells.