Successful completion of first riser-drilling operations in earthquake zoneJuly 31, 2009Drilling operations in earthquake zone July 30, 2009-Kumano Basin off Kii Peninsula, approximately 58 km southeast of Japan- Despite harsh weather and ocean conditions, and complex geological characteristics of its drill site, the deep-sea drilling vessel CHIKYU, for the first time in the history of scientific ocean drilling, conducted riser-drilling operations to drill successfully down to a depth of 1,603.7 meters beneath the seafloor (at water depth of 2,054 meters). Engaged in the Integrated Ocean Drilling Program (IODP) Expedition 319, the CHIKYU is drilling deep into the upper portion of the great Nankai Trough earthquake zone to gain insights into geological formations and stress-strain characteristics. The CHIKYU is operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) a partner in the IODP. The Kumano Basin drilling and sampling operations began on May 12; the science party, which includes Co-Chief Scientist Lisa McNeill of the National Oceanography Centre, Southampton (UK), is expected to complete the first drill site on or about August 1. Riser-drilling technology was used from about 700 meters below the seafloor to the bottom of the hole. Riser-drilling involves the circulation of drilling fluid that helps maintain pressure balance within the borehole. Cuttings were recovered from the circulated drilling fluid and analyzed to gain a better overall picture of downhole changes in lithology and age. Core samples also were collected between depths of 1,510 and 1,593.3 meters below the seafloor. Co-Chief Scientist Lisa McNeill, a member of the University of Southampton's School of Ocean and Earth Science based at the National Oceanography Centre, states: "This state-of-the-art technology enables scientists to access an unknown area. It will provide a lot of important information about what has happened in the seismogenic zone in the past and its present condition." She adds, "I'm very pleased to be a member of the science party conducting the first riser-drilling operation in the Nankai Trough." Following drilling operations that included 'measurement-while-drilling' to obtain real-time geophysical characteristics, wireline logging instruments were lowered into the borehole to measure formation temperature, resistivity, porosity, density, gamma ray, and borehole diameter. The riser-drilling technology enabled dynamic formation testing using the logging instrumentation for the first time during IODP scientific ocean drilling operations; this instrumentation is designed to measure stress, water pressure, and rock permeability. Co-Chief Scientist Timothy Byrne of University of Connecticut emphasises the importance of the Nankai Trough experiment results. "These two parameters , stress magnitude and pore pressure," he says, "are both important to understanding earthquake processes." In addition, vertical seismic profiling was conducted from July 24-25 to obtain accurate details of the geological structure of the plate boundary system. The activity involved an array of 16 seismographs vertically lowered into the borehole and eight ocean-bottom seismographs placed on the seafloor. An air-gun array on the JAMSTEC research vessel KAIREI generated elastic waves, which traveled through the formation to be recorded on the borehole and seafloor instruments. "The seismic sensor array was installed in this hole below the thick sediment layer," says Co-Chief Scientist Eiichiro Araki of JAMSTEC: "It acts like a telescope exploring the structure of faults in detail, which are responsible for causing large earthquakes such as the one that occurred here in 1944." Operations at this drill site are expected to conclude after casing the borehole to the bottom of the hole and capping it with a corrosion cap for future installation of a long-term borehole monitoring system (LTBMS). After completion of this task, the CHIKYU will move to its next drill site, where riserless drilling will be employed to penetrate the shallow portion of the megasplay fault branching from the seismogenic zone. Logging-while-drilling (LWD) will be conducted to measure rock properties, geological formation, and geophysical characteristics of the area. As a preliminary operation for LTBMS scheduled in the future, observatory instruments will be installed inside the hole to measure borehole temperature and pressure over the next few years. Further analyses by scientists are expected to generate significant scientific knowledge of past earthquake activities and development processes of the Nankai Trough accretionary prism, as well as the mechanism of occurrence of large earthquakes and tsunamis. Co-Chief Scientist Demian Saffer of The Pennsylvania State University notes, "With the efforts of the drillers and operations groups, we succeeded in conducting several very challenging experiments, many of which can only be achieved by riser drilling. The results provide important information about conditions within the rocks above zones where earthquakes occur. Ultimately, we plan to install long-term observatory systems in these boreholes that will allow us to continuously monitor the geologic formation during the earthquake cycle." National Oceanography Centre, Southampton (UK) |
|||||||||||||||||||||
| Related Drilling Current Events and Drilling News Articles Tiny bubbles clean oil from water Small amounts of oil leave a fluorescent sheen on polluted water. Oil sheen is hard to remove, even when the water is aerated with ozone or filtered through sand. Researchers Hail Innovative Plan to Save Rainforest, Reduce Greenhouse Gas Emissions An innovative proposal by the Ecuadorian government to protect an untouched, oil rich region of Amazon rainforest is a precedent-setting and potentially economically viable approach, says a team of environmental researchers from the University of Maryland, the World Resources Institute and Save America's Forests. Study uses satellite imagery to identify active magma systems in East Africa's Rift Valley A team from the University of Miami, University of El Paso and University of Rochester have employed Interferometric Synthetic Aperture Radar (InSAR) images compiled over a decade to study volcanic activity in the African Rift. The study, published in the November issue of Geology, studies the section of the rift in Kenya. Tsunami waves reasonably likely to strike Israel "There is a likely chance of tsunami waves reaching the shores of Israel," says Dr. Beverly Goodman of the Leon H. Charney School of Marine Sciences at the University of Haifa following an encompassing geo-archaeological study at the port of Caesarea. "Tsunami events in the Mediterranean do occur less frequently than in the Pacific Ocean, but our findings reveal a moderate rate of recurrence," she says. As Greenland melts Not that long ago - the blink of a geologic eye - global temperatures were so warm that ice on Greenland could have been hard to come by. Today, the largest island in the world is covered with ice 1.6 miles thick. Even so, Greenland has become a hot spot for climate scientists. Fracture zones endanger tombs in Valley of Kings Ancient choices made by Egyptians digging burial tombs may have led to today's problems with damage and curation of these precious archaeological treasures, but photography and detailed geological mapping should help curators protect the sites, according to a Penn State researcher. New study provides insight on energy development and sage-grouse habitat in the intermountain West A study released October 14th in the current issue of the peer-reviewed journal PLoS ONE will shed new light on oil and gas development potential in the Intermountain West. Scientists obtain rocks moving into seismogenic zone An international group of scientists aboard the Deep-Sea Drilling Vessel CHIKYU, operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) for the Integrated Ocean Drilling Program (IODP), return from a 40-day scientific expedition off the shore of the Kii Peninsula, Japan on Oct. 10, 2009. Algae and pollen grains provide evidence of remarkably warm period in Antarctica's history For Sophie Warny, LSU assistant professor of geology and geophysics and curator at the LSU Museum of Natural Science, years of patience in analyzing Antarctic samples with low fossil recovery finally led to a scientific breakthrough. Unlocking the secrets of the seafloor: The future of scientific ocean drilling Close to 600 scientists from 21 countries met Sept. 23 - 25 2009 in Bremen, Germany, to outline major scientific targets for a new and ambitious ocean drilling research program. More Drilling Current Events and Drilling News Articles |
|||||||||||||||||||||
|
|||||||||||||||||||||
|
|||||||||||||||||||||