Sea Technology

SEP 2016

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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10 st / September 2016 www.sea-technology.com A s oil and gas and mineral exploration expands fur- ther into deeper water, the effects of water depth on geotechnical in-situ testing and core recovery have become more and more pronounced. Historically, shallow-water investigation has been conducted from a barge or drill ship. In this configuration any core recovery or in-situ geotechnical evaluation, includ- ing CPTu, Vane Shear and T-Bar tests, have required the drill string to be constructed from the vessel and through the full water column in order to initiate test- ing. In water depths of tens or even hundreds of meters this timing cost may be acceptable; however, the time required and costs associated rise nonlinearly with wa- ter depth and offer no value to the required data col- lection. Deeper water exploration offers greater benefit to both enhanced oil recovery techniques and economies of scale. This results in an increased demand for sub- sea installed hardware on deepwater developments, including seabed template sets, riser bases, PLETs, PLEMs and other associated equipment, all of which require some level of geotechnical investigation for their design. As a result, the costs savings and improve- ments in accuracy and reliability for sampling and in- situ geotechnical testing at deepwater sites have be- come increasingly important. In the past decade, increasing focus has been placed on the use of seafloor drill systems to replace surface-driven conventional drilling and geotechnical evaluation approaches. Seafloor-based systems offer significant advantages as the depth required for evalu- ation (typically between 30 to 60 m) becomes an ever smaller portion of the total water depth. A study con- ducted on the Norwegian Sea Luva Gas Field in 2009 showed that for a 40-m bore hole, a seafloor drilling system showed improved timing efficiency over a sur- face-based drilling campaign in water depths of only 130 m, and at depths of approximately 1,300 m a sea- floor drilling solution is three to 10 times more efficient for core recovery and CPT. While the efficiency and total operating cost of a seafloor drill over a surface- based system for drilling or in-situ geotechnical evalu- ation is unquestionably improved in deepwater, the CRD100 Seafloor Geotechnical Drill Designing an Integrated System Beyond ROV 'Tooling Package' By Eric Jackson • Derek White • Allan Spencer Returning the CRD100 drill to ship for sample recovery.

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