1
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Simple, affordable, and sustainable borehole observatories for complex monitoring objectives

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Abstract. Seafloor drill rigs are remotely operated systems that provide a cost-effective means to recover sedimentary records of the upper sub-seafloor deposits. Recent increases in their payload included downhole logging tools or autoclave coring systems. Here we report on another milestone in using seafloor rigs: the development and installation of shallow borehole observatories. Three different systems have been developed for the MARUM-MeBo (Meeresboden-Bohrgerät) seafloor drill, which is operated by MARUM, University of Bremen, Germany. A simple design, the MeBoPLUG, separates the inner borehole from the overlying ocean by using o-ring seals at the conical threads of the drill pipe. The systems are self-contained and include data loggers, batteries, thermistors and a differential pressure sensor. A second design, the so-called MeBoCORK (Circulation Obviation Retrofit Kit), is more sophisticated and also hosts an acoustic modem for data transfer and, if desired, fluid sampling capability using osmotic pumps. In these MeBoCORKs, two systems have to be distinguished: the CORK-A (A stands for autonomous) can be installed by the MeBo alone and monitors pressure and temperature inside and above the borehole (the latter for reference); the CORK-B (B stands for bottom) has a higher payload and can additionally be equipped with geochemical, biological or other physical components. Owing to its larger size, it is installed by a remotely operated underwater vehicle (ROV) and utilises a hot-stab connection in the upper portion of the drill string. Either design relies on a hot-stab connection from beneath in which coiled tubing with a conical drop weight is lowered to couple to the formation. These tubes are fluid-saturated and either serve to transmit pore pressure signals or collect porewater in the osmo-sampler. The third design, the MeBoPUPPI (Pop-Up Pore Pressure Instrument), is similar to the MeBoCORK-A and monitors pore pressure and temperature in a self-contained manner. Instead of transferring data on command using an acoustic modem, the MeBoPUPPI contains a pop-up telemetry with iridium link. After a predefined period, the data unit with satellite link is released, ascends to the sea surface, and remains there for up to 2 weeks while sending the long-term data sets to shore. In summer 2012, two MeBoPLUGs, one MeBoCORK-A and one MeBoCORK-B were installed with MeBo on RV Sonne, Germany, in the Nankai Trough area, Japan. We have successfully downloaded data from the CORKs, attesting that coupling to the formation worked, and pressure records were elevated relative to the seafloor reference. In the near future, we will further deploy the first two MeBoPUPPIs. Recovery of all monitoring systems by a ROV is planned for 2016.

          Related collections

          Most cited references12

          • Record: found
          • Abstract: not found
          • Article: not found

          Correlated transient fluid pulsing and seismic tremor in the Costa Rica subduction zone

            Bookmark
            • Record: found
            • Abstract: not found
            • Article: not found

            Long-term hydrogeochemical records in the oceanic basement and forearc prism at the Costa Rica subduction zone

              Bookmark
              • Record: found
              • Abstract: not found
              • Article: not found

              Theory for the propagation of tidally induced pore pressure variations in layered subseafloor formations

                Bookmark

                Author and article information

                Journal
                Geoscientific Instrumentation, Methods and Data Systems
                Geosci. Instrum. Method. Data Syst.
                Copernicus GmbH
                2193-0864
                2015
                May 18 2015
                : 4
                : 1
                : 99-109
                Article
                10.5194/gi-4-99-2015
                9f243ea0-adf0-42a0-9db7-dbffcae0986d
                © 2015

                https://creativecommons.org/licenses/by/3.0/

                History

                Comments

                Comment on this article