Underwater monitoring network: Using the deep-sea Drill MARUM-MeBo for installing Subseafloor Sensor Systems for monitoring Seafloor Intervention Operations

摘要

Any intervention into the seafloor will have an impact on the structural integrity of the material in theaffected region and will hence result in variation in stress, pore water pressure, and temperature. As aconsequence fluids maybe mobilized and may in turn affect the intervention process. To closely track suchprocesses or monitor safe operations in areas of e.g. hydrocarbon exploitation, seafloor mining or marinerenewables, new measuring strategies have to be developed to allow a spatio-temporal coverage via asensor network. With the deep-sea drill MARUM-MeBo that has been developed at the University ofBremen/MARUM new opportunities are opened up to deploy sensors in shallow boreholes (on80 msub-seafloor depth). MeBo is characterized by its versatility and high mobility with deployments down towater depths of 2000 m. Materials recovered via wire-line coring technique included both soft sedimentsand hard rocks. After drilling a 2.35 m section the core is recovered using a wire that is latched to the innercore barrel with an overshot. The outer drill string stays in the drilled hole during the entire drillingprocess. Recently, simple self-contained borehole instruments were developed that are placed in the hole,in which the outer drill string serves as casing. We propose to employ MeBo to deploy a network ofinstrumented boreholes in the region of deep-sea interventions to monitor the environmental conditionscontinuously over long time intervals. Data can be exchanged via acoustic modems and may serve toarchive time series and use in hazard assessment and early warning.