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

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 selfcontained 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.

Listening Down the Pipe

“…"CORK-Lite" models that can be deployed by remotely operated vehicles allow installation of instrumentation in existing reentry boreholes without the aid of a drillship (e.g., Wheat et al, 2012), and some designs include the simple Smart and Genius plugs that permit temporary monitoring of a zone of interest (Kopf et al, 2011). With portable rock drills now used as mission-specific platforms in IODP, deployment of subseafloor observatories will also be possible from ships of opportunity (e.g., Kopf et al, 2015) and in regions where the drillships JOIDES Resolution and Chikyu cannot operate.…”

A Rule-Based Reasoner for Underwater Robots Using OWL and SWRL

“…The communication link of acoustic uses an acoustic modem and is able to offer the possibility of wireless communication under water for Autonomous Underwater Vehicles (AUVs) [ 53 ]. The communication link of radio and satellite can be used by Remotely Operated Vehicles (ROVs) to transmit data and commands between vehicles and operators [ 54 , 55 ]. If the environment is terrible and the communication is easily disturbed by noise, the communication link of cable is then a reliable option [ 56 ].…”

Real-time monitoring instrument designed for the deformation and sliding period of colluvial landslides

“…The assessment of landslide behavior is usually undertaken via real-time monitoring (Liu et al 2004;Yin et al 2010;Tuccimei et al 2015;Kopf et al 2015;Zhao et al 2015). A method is suggested (Crosta and Agliardi 2003) to forecast slope failures and to assess alert velocity thresholds using monitoring data.…”