January 2012 Issue
NSF Highlights Advancements in the Integrated Ocean Drilling Program
By Thomas Janecek
Division of Ocean Sciences
National Science Foundation
The sediments underlying the ocean floors contain high-resolution records of the Earth's history. Throughout the past 40 years, scientific ocean drilling has helped unlock that history while providing answers to fundamental scientific questions about natural hazards, climate change, volcanic eruptions, and mineral and energy resources. Many of these drilling efforts were pioneered by research and infrastructure supported by the National Science Foundation (NSF), such as Project Mohole (1961 to 1966), the Deep Sea Drilling Project (1968 to 1983) and the Ocean Drilling Program (1958 to 2003).
The Integrated Ocean Drilling Program (IODP), begun in 2003 and supported by the NSF and 23 other countries, has built upon the successes of the earlier scientific drilling and technology efforts. The IODP continues to revolutionize our view of Earth history and global processes through ocean basin exploration.
The NSF and Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT) are the lead agencies for IODP.
IODP utilizes a number of drilling platforms. Included in the program are the JOIDES Resolution, a nonriser vessel supported by the NSF; DV Chikyu, a riser-drilling vessel supported by MEXT; and mission-specific platforms—rom jack-up rigs to drilling-rig outfitted icebreakers—provided by the European Consortium for Ocean Research Drilling (ECORD).
The JOIDES Resolution. Also known as the JR, this vessel is operated by the U.S. Implementing Organization and is renowned for its global capability, versatility and operational flexibility. The JR can operate in water depths from 75 to 8,200 meters, with as much as 2 kilometers of subseafloor penetration. After 133 scientific drilling expeditions, the JR underwent a $115 million renovation supported by the NSF and came back into service in 2009. This comprehensive renovation, which extended the JR's life by 20 years, included the replacement of all structures forward of the derrick as well as the upgrade or replacement of all major drilling and downhole logging systems. A new multifloor laboratory was installed, and the majority of the science systems were renovated or replaced. The ship now holds state-of-the-art analytical equipment for onboard core descriptions and equipment for a wide variety of microbiological, geotechnical and analytical chemistry investigations.
In the three years since its renovation, the JR has shown its versatility, with global operations that include high-resolution paleoceanographic expeditions, investigations into the evolution and formation of a large igneous province, mantle dynamics, global sea-level change, Antarctic glaciation history, subseafloor hydrogeology and microbiology. Its new drilling capabilities have directly led to scientific coring penetration records, including the deepest scientific ocean sediment hole drilled to 1,928 meters. On each expedition, a staff of about 50 scientists and technicians process the core and completely characterize the recovered material by conducting detailed chemical, geotechnical and microbiological analyses.
Major deep-sea drilling and coring can be conducted in either closed-hole (riser) or open-hole (riserless) modes. Click to enlarge.
The DV Chikyu. This Japanese vessel has added a deep-drilling capability to scientific ocean drilling. Chikyu, operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Center for Deep Earth Exploration, can handle up to 12 kilometers of drill string and has a riser capable of drilling in 2.5 kilometers of water. Chikyu's on-board laboratory is equipped with a suite of state-of-the-art analytical equipment for core analyses (including a CT scanner). Chikyu's riser technology, which provides mud circulation to clear drill cuttings and stabilizes the borehole, enables deep penetration into unstable formations, allowing sampling of active fault zones and downhole measurements of pore pressure and stress. Since 2005, Chikyu has drilled deep holes in the Nankai subduction zone off the eastern cost of Japan, an area with a 1,400-year-long recorded history of magnitude 8-plus earthquakes recurring at 120-year intervals. Chikyu was damaged by the tsunami during the 2011 Tohoku earthquake but has been repaired and is now drilling again.
Mission-Specific Platforms. Implemented by the ECORD Science Operator, mission-specific platforms (MSPs) are conducted on a case-by-case basis to meet unique oceanographic or environmental requirements that the larger IODP platforms cannot address, such as shallow-water conditions (e.g., less than 75 meters' depth) and high-latitude ice-covered areas. Four MSP expeditions have been conducted since 2004, each employing a different drilling strategy and platform type. The first MSP operation, in the high Arctic, utilized three icebreakers: two vessels to break up the ice and a third DP vessel outfitted with a drilling system, which allowed it to core the Lomonosov Ridge in the Arctic Ocean in 1,300 meters of water to 400 meters below the seafloor.
Another MSP expedition on the New Jersey continental shelf in 2009 employed a three-legged lift boat to keep the drilling platform above the waves. Working in 35 meters of water, this operation successfully cored and recovered sediments more than 750 meters below the seafloor in loosely consolidated shelf sediments.
Two other MSP expeditions worked in the shallow-reef environments of Tahiti and the Great Barrier Reef in 2005 and 2010, respectively, to recover ultrahigh-resolution sea-level records. In both cases, DP drilling vessels outfitted with drilling rigs were able to successfully core and recover coralline material in environmentally sensitive areas. Unlike the larger IODP platforms, these MSP operations employ only a small shipboard party to collect initial ephemeral data on the cores. Following the expeditions, the cores were shipped back to an IODP repository, where detailed follow-up work was conducted by about 30 scientists.
Borehole CORK Measurements
While cores are the backbone of IODP science, the scientific drilling community has recognized the need to collect in-situ measurements in the boreholes. The desire to elucidate crustal processes, define oceanic geochemical budgets and investigate the subsurface biosphere harbored in oceanic crust has led to the NSF-supported development of long-term subseafloor borehole observatories outfitted with fluid-samplers and temperature and pressure data loggers that often extend hundreds of meters below the seafloor.
Circulation obviation retrofit kits (CORKs) are installed by a drillship after a borehole is completed. Valves that access downhole fluid samplers and data loggers for pressure and temperature measurements are located on the wellhead for access by submersibles or ROVs. These samplers provide pristine fluids, allowing scientists to monitor physical, chemical and biological changes. CORKs have been deployed in a sedimented midocean ridge, in the flanks of midocean ridges and on convergent margins during 13 drilling expeditions. In the fall of 2011, the JR retrieved a CORK emplaced nearly 15 years ago, downloading years of data, and installed new CORKs on the Mid-Atlantic Ridge to further understanding of the extent of microbial colonization in the subseafloor, the diversity and activity of this crustal biome, and microbial activity's role in modulating geochemical exchange between the Earth's crust and ocean.
While standard oil and gas logging tools are often utilized by IODP, program requirements for slimhole designs, high-temperature environments and ultrahigh-resolution characterization of thin beds have led to the NSF-supported development of state-of-the-art wireline and logging-while-drilling sondes by the program's engineers.
The scientific ocean drilling community, through NSF and the other international IODP funding agencies, is actively pursuing funding to expand this ambitious exploration program beyond 2013. The international scientific drilling community has developed a scientific plan for the next decade. The new plans set forth a program to conduct expeditions that will target pressing questions about climate and ocean change, biodiversity and the limits of deep life, and the processes associated with geohazards on human time scales.
Achieving these goals will require a wide variety of drilling capabilities, in-situ measurements and long-term monitoring capabilities, including deep drilling up to 7 kilometers into the ocean floor, at continental margins, and in extreme environments such as shallow water (less than 100 meters) and the Arctic.
No single drilling platform or coring technique can accomplish this task. The next phase of ocean drilling, if successfully funded, will continue to use the two principal platforms, the JR and the Chikyu, complemented by the use of mission-specific platforms. With a planned development of Chikyu's riser capability from 2.5 kilometers to more than 4 kilometers of water depths, along with new generations of advanced CORKs to isolate and sample multiple subsurface zones and continued development of coring and logging tool, the new program will have the necessary technology to continue its unparalleled exploration of the Earth beneath the sea.