Characteristic Settling Time and Interface Height Dependence on Pore Fluid Chemistry for Sediment Collected From Area B, During India's National Gas Hydrate Program Expedition NGHP-02

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What does this data set describe?

Title:
Characteristic Settling Time and Interface Height Dependence on Pore Fluid Chemistry for Sediment Collected From Area B, During India's National Gas Hydrate Program Expedition NGHP-02
Abstract:
One goal of the Indian National Gas Hydrate Program's NGHP-02 expedition was to examine the geomechanical response of marine sediment to the extraction of methane from gas hydrate found offshore eastern India in the Bay of Bengal. Methane gas hydrate is a naturally occurring crystalline solid that sequesters methane in individual molecular cages in a lattice of water molecules. Methane gas hydrate is a potential energy resource, but whether extracting methane from gas hydrate in the marine subsurface is technically and economically viable remains an open research topic as of 2018. This data release provides insight about a poorly quantified aspect of this process: the reaction of fine-grained sediment particles (fines) to the change in pore water chemistry that occurs when methane is extracted from gas hydrate. Fines are an issue for production because they can get resuspended in the flow of fluid and gas toward the extraction well. As fines move, they can cluster and subsequently clog pore throats in the sediment, reducing permeability (which controls how easily methane can flow toward the extraction well). There are two main factors in determining the cluster structure (the size and fabric of the cluster) and the cluster formation and settling rates: the type of fine-grained particle and the chemistry of the surrounding pore water. Data in this study provide insight into both factors.
Fine particles interact with each other primarily in response to electrical forces, and changes in pore water chemistry can significantly alter how those forces are communicated between particles. In marine systems, in situ pore water is an electrically conductive brine. As gas hydrate dissociates, however, fresh water is released along with the methane, making the pore water less conductive. Depending on the type of fine-grained particles involved, the pore water chemistry change enhances or diminishes the clustering and changes the rates at which the clusters form and settle.
For this data release, specimens from the NGHP-02 expedition are observed during sedimentation (settling) tests in pore fluids of differing chemistry. The results included in this data release can (1) provide insight into the types of fines present, which can be difficult to quantify if using the more standard x-ray diffraction method for identifying fines and (2) indicate whether the in situ fines are likely to increase or decrease their capacity to clog pore throats as the pore water transitions from higher to lower salinity during gas hydrate dissociation.
Supplemental_Information:
In addition to funding from the U.S. Geological Survey Gas Hydrate Project, this work is sponsored in part by the Department of Energy, both through an interagency agreement (DE-FE0026166) and a grant awarded to Louisiana State University (DE-FE0028966). More information about the project can be found at: https://www.netl.doe.gov/research/oil-and-gas/project-summaries/methane-hydrate/fe0028966-lsu-fe0026166-usgs. This work is also part of the NGHP-02 expedition. Links to related data and publications within the NGHP-02 project are collected in the USGS Field Activity Report 2015-023-FA, found at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2015-023-FA.
  1. How might this data set be cited?
    Jang, Junbong, 2018, Characteristic Settling Time and Interface Height Dependence on Pore Fluid Chemistry for Sediment Collected From Area B, During India's National Gas Hydrate Program Expedition NGHP-02: data release DOI:10.5066/P9FXJ1VX, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Jang, Junbong, Waite, William F., Stern, Laura A., Collett, Timothy S., and Kumar, Pushpendra, 2018, Dependence of Sedimentation Behavior on Pore-Fluid Chemistry for Sediment Collected From Area B, Krishna-Godavari Basin During India's National Gas Hydrate Program, NGHP-02: data release DOI:10.5066/P9FXJ1VX, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Jang, J., Waite, W.F., Stern, L.A., Collett T.S., and Kumar, P., 2018, Dependence of sedimentation behavior on pore-fluid chemistry for sediment collected from Area B, Krishna-Godavari Basin, during India's National Gas Hydrate Program, NGHP-02: U.S. Geological Survey data release, https://doi.org/10.5066/P9FXJ1VX.
    This dataset supports the following publication:
    Jang, J., Waite, W.F., Stern, L.A., Collett T.S., and Kumar, P., 2018, Field- to grain-scale physical property characterization of gas hydrate-bearing reservoir and associated seal sediment collected during NGHP-02 in the Krishna-Godavari Basin, Area B: Marine and Petroleum Geology, https://doi.org/10.1016/j.marpetgeo.2018.09.027.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: 84.19200167
    East_Bounding_Coordinate: 84.19757167
    North_Bounding_Coordinate: 17.43830167
    South_Bounding_Coordinate: 17.43391500
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5b228193e4b092d9652a211d?name=NGHP02_AreaB_T50_FinalInterfaceHeight_BrowseGraphic.png (PNG)
    Normalized interface height dependence on pore fluid chemistry for each specimen (Depositional interface, open symbols; Accumulation interface, solid symbols, X-axis shows the specimen ID numbers).
    https://www.sciencebase.gov/catalog/file/get/5b228193e4b092d9652a211d?name=LandingPage_BrowseGraphic.png (PNG)
    Four sediment settling tubes, imaged at the end of the sedimentation test for the fine reservoir sand. From left to right, the settling fluid is: freshened pore water (DWF), dissolved salt water (DSW), 2-Molar brine and kerosene. The accumulation and depositional interfaces tracked in this data release are defined as follows: accumulation interface (white arrows) separates the settled particles from the overlying particles that have yet to settle; the depositional interface (yellow arrows) separates the cloudy, particle-filled fluid from the overlying clear fluid out of which the particles have already settled.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 18-May-2015
    Ending_Date: 27-May-2015
    Currentness_Reference:
    ground condition of the field activity when the samples were collected
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set.
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in decimal degrees. The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Meters below sea floor
      Depth_Resolution: 1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    NGHP02_AreaB_T50_FinalInterfaceHeight_Metadata
    Time required to reach halfway from the initial and final interface heights (t50) and normalized final depositional and accumulated sediment interface heights of NGHP-02 (Krishna-Godavari Basin, offshore India) sediment specimens allowed to settle in various fluids. (Source: U.S. Geological Survey)
    Site
    Site: NGHP-02 site name designation. Format is: Expedition Name (NGHP-02)-Site Number and Hole Designation Letter. Hole A was used only for logging-while-drilling (no core recovery). Holes B and C were used for coring. (Source: U.S. Geological Survey) Character set (text).
    J-CORES sample ID
    sampleID: Unique, sequential identifier given at the time of collection to any shipboard subsample taken for any measurement type. Specimens were collected on the D/V Chikyu, so each ID begins with CKY. (Source: Shipboard science party, D/V Chikyu) Character set (text).
    Latitude (degrees, minutes, seconds)
    Latitude_DMS: Latitude coordinate, in degrees (°) minutes (’) decimal seconds (”), of the sample’s location. North latitude recorded as positive values. (Source: Shipboard science party, D/V Chikyu)
    Range of values
    Minimum:17°26'02.094"
    Maximum:17°26'17.886"
    Units:degrees (°) minutes (’) decimal seconds (”)
    Longitude (degrees, minutes, seconds)
    Longitude_DMS: Longitude coordinate, in degrees (°) minutes (’) decimal seconds (”), of the sample’s location. East longitude is recorded as positive values. (Source: Shipboard science party, D/V Chikyu)
    Range of values
    Minimum:84°11'31.206"
    Maximum:84°11'51.258"
    Units:degrees (°) minutes (’) decimal seconds (”)
    Latitude (decimal degrees)
    Lat_DD: Latitude coordinate, in decimal-degrees, of sample’s location. North latitude recorded as positive values. (Source: U.S. Geological Survey)
    Range of values
    Minimum:17.43391500
    Maximum:17.43830167
    Units:decimal degrees
    Longitude (decimal degrees)
    Long_DD: Longitude coordinate, in decimal degrees, of the sample’s location. East longitude is recorded as positive values. (Source: U.S. Geological Survey)
    Range of values
    Minimum:84.19200167
    Maximum:84.19757167
    Units:decimal degrees
    Average Depth (m CSF-A), mbsf
    CSFA_Depth_mbsf: Depth of sample in meters below the sea floor (mbsf), using the CSF-A convention in which gas expansion gaps, if present, are included in the depth. (Source: Shipboard science party, D/V Chikyu)
    Range of values
    Minimum:262.96
    Maximum:286.25
    Units:meters
    Average Depth (m CSF-B), mbsf
    CSFB_Depth_mbsf: Depth of sample in meters below the sea floor (mbsf), using the CSF-B convention in which gas expansion gaps, if present at the time of core recovery, have been removed. (Source: Shipboard science party, D/V Chikyu)
    Range of values
    Minimum:262.60
    Maximum:285.62
    Units:meters
    Sediment Type
    Sed_Type: Description of which lithology is represented by the specimen. The five lithology descriptions are given in the enumerated domain definitions. (Source: U.S. Geological Survey)
    ValueDefinition
    Reservoir: Fine SandThe find sand layer where gas hydrate is primarily hosted.
    Reservoir: Clay InterbedFine-grained sediment with little-to-no gas hydrate that is interbedded with the fine sand layer.
    Reservoir: Sandy InterbedTransition between the two lithologies of find sand (Reservoir: Fine Sand) and find-grained sediment (Reservoir: Clay Interbed)
    Overburden SealFine-grained sediment that bounds the top of the gas hydrate-bearing reservoir.
    Underlying SealFine-grained sediment that bounds the base of the gas hydrate-bearing reservoir.
    t50, Depositional Interface, Freshened Water, min
    DWF_t50_DepInt_min: Each entry is the time required for the sediment to settle halfway from its initial to its final height. Blank entries indicate the depositional interface was not distinguishable for that row (specimen). As described in the process steps, the original specimen is dried, then saturated with deionized water to create the DWS specimen. That specimen is tested, then approximately 80% of the supernatant fluid in the cylinder was removed after the initial sedimentation test. The cylinder was refilled with deionized water, so the mixture contained freshened water and was identified as a “deionized water, freshened” sample (DWF). Thus, the DWF specimen is considered to be the test with the freshest (lowest salt content) water. Only the Reservoir-Clay Interbed had a continusouly-observable depositional interface. (Source: U.S. Geological Survey)
    Range of values
    Minimum:100
    Maximum:100
    Units:minutes
    t50, Accumulation Interface, Freshened Water, min
    DWF_t50_AccInt_min: Each entry is the time required for the acculumated interface to build up to half of the final accumulated interface height. Blank entries indicate the accumulation interface was not distinguishable for that row (specimen). As noted above, the DWF specimen is considered to have the freshest (lowest salt concentration) water. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.7
    Maximum:60
    Units:minutes
    t50, Depositional Interface, Dissolved Salt Water, min
    DWS_t50_DepInt_min: Each entry is the time required for the sediment to settle halfway from it's initial to its final height. Blank entries indicate the depositional interface was not distinguishable for that row (specimen). Sediment is mixed with deionized water to obtain these data. As described in the process steps, the original specimen is dried, then saturated with deionized water to create the DWS specimen. Because the salts in the original specimen remain in the specimen for this test, this specimen has a higher salt content than the DWF specimen. Because of the amount of fluid used for the settling test compared to the amount of sediment, the DWS fluid has a salinity that is less than the in situ salinity, however. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.7
    Maximum:20
    Units:minutes
    t50, Accumulation Interface, Dissolved Salt Water, min
    DWS_t50_AccInt_min: Each entry is the time required for the acculumated interface to build up to half of the final accumulated interface height. Blank entries indicate the accumulation interface was not distinguishable for that row (specimen). As noted above, the DWS specimen is considered to have a higher salt content (salinity) than the DWF specimen, but less than the in situ salinity. (Source: U.S. Geological Survey)
    Range of values
    Minimum:2
    Maximum:3
    Units:minutes
    t50, Depositional Interface, 2M Brine, min
    2M_t50_DepInt_min: Each entry is the time required for the sediment to settle halfway from it's initial to its final height. Sediment is mixed with brine (2M NaCl) to obtain these data. Because this test is run on the original sediment after drying, the specimen still contains the salt from the in situ environment. This salt is then dissolved in the 2M brine, so the final salinity is higher than 2M. The 2M Brine specimen has the highest salinity of any of the specimens tested here. There is no corresponding column for the t50 accumulated interface because only the depositional interface was distinguishable for specimens in 2M brine. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.7
    Maximum:20
    Units:minutes
    t50, Depositional Interface, Kerosene, min
    Kerosene_t50_DepInt_min: Each entry is the time required for the sediment to settle halfway from it's initial to its final height. There is no corresponding column for the t50 accumulated interface because only the depositional interface was distinguishable for specimens in kerosene. Sediment is mixed with kerosene to obtain these data. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.5
    Maximum:0.65
    Units:minutes
    NormHeight, Depositional Interface, Freshened Water
    DWF_DepNormHeight: These normalized final interface heights correspond to the interfaces described in the t50 columns. Blank entries indicate the depositional interface was not distinguishable for that row (specimen). To normalize the interface height, the final height of the interface is divided by the initial specimen height before fluid was introduced into the settling chamber (25.4 mm). High values tend to indicate looser, more porous sediment fabric. As described above, the DWF specimen is considered to be the test with the freshest (lowest salt content) water. Only the Reservoir-Clay Interbed had a continusouly-observable depositional interface. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1.525
    Maximum:1.525
    Units:unitless
    NormHeight, Accumulation Interface, Freshened Water
    DWF_AccNormHeight: These normalized final interface heights correspond to the interfaces described in the t50 columns. Blank entries indicate the accumulation interface was not distinguishable for that row (specimen). To normalize the interface height, the final height of the interface is divided by the initial specimen height before fluid was introduced into the settling chamber (25.4 mm). High values tend to indicate looser, more porous sediment fabric. As noted above, the DWF specimen is considered to have the freshest (lowest salt concentration) water. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.975
    Maximum:1.475
    Units:unitless
    NormHeight, Depositional Interface, Dissolved Salt Water
    DWS_DepNormHeight: These normalized final interface heights correspond to the interfaces described in the t50 columns. Blank entries indicate the depositional interface was not distinguishable for that row (specimen). To normalize the interface height, the final height of the interface is divided by the initial specimen height before fluid was introduced into the settling chamber (25.4 mm). High values tend to indicate looser, more porous sediment fabric. As described above, this specimen has a higher salt content than the DWF specimen, but less than the in situ salinity. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1.2
    Maximum:1.25
    Units:unitless
    NormHeight, Accumulation Interface, Dissolved Salt Water
    DWS_AccNormHeight: These normalized final interface heights correspond to the interfaces described in the t50 columns. Blank entries indicate the accumulation interface was not distinguishable for that row (specimen). To normalize the interface height, the final height of the interface is divided by the initial specimen height before fluid was introduced into the settling chamber (25.4 mm). High values tend to indicate looser, more porous sediment fabric. As noted above, the DWS specimen is considered to have a higher salt content (salinity) than the DWF specimen, but less than the in situ salinity. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:1.5
    Units:unitless
    NormHeight, Depositional Interface, 2M Brine
    2M_DepNormHeight: These normalized final interface heights correspond to the interfaces described in the t50 columns. To normalize the interface height, the final height of the interface is divided by the initial specimen height before fluid was introduced into the settling chamber (25.4 mm). High values tend to indicate looser, more porous sediment fabric. As noted above, the 2M Brine specimen has the highest salinity of any of the specimens tested here. There is no corresponding column for the accumulated interface normheight because only the depositional interface was distinguishable for specimens in 2M brine. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1.05
    Maximum:1.451
    Units:unitless
    NormHeight, Depositional Interface, Kerosene
    Kerosene_DepNormHeight: These normalized final interface heights correspond to the interfaces described in the t50 columns. To normalize the interface height, the final height of the interface is divided by the initial specimen height before fluid was introduced into the settling chamber (25.4 mm). High values tend to indicate looser, more porous sediment fabric. There is no corresponding column for the accumulated interface normheight because only the depositional interface was distinguishable for specimens in kerosene. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1.24
    Maximum:1.4
    Units:unitless
    Entity_and_Attribute_Overview:
    These data are available in a Microsoft Excel XLSX as well as a CSV format. The first two rows in the XLSX file are header rows, where the second row is an abbreviated column label intended for software packages that are unable to cope with longer labels available in the first row of the XLSX file. The first part of the attribute definition (before the colon) indicates the abbreviated column label. The first row of the CSV file is a header line and is the same as the abbreviated column label on the second row of the XLSX file.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Junbong Jang
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Junbong Jang
    Geophysicist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2278 (voice)
    508-457-2310 (FAX)
    jjang@usgs.gov

Why was the data set created?

The purpose of this dataset is to establish the characteristic settling times and the fabric of the settling particles after approximately four days. The t50 time, the time to obtain 50 percent of the final interface height, captures the settling rate as a function of pore-fluid chemistry. The final interface heights indicate the fabric of the sediment that settled (e.g. high final interface heights indicate the particles settled in a loose, high-porosity fabric). Results presented here are used to support discussions of anticipated behaviors in the natural system offshore India as presented in the related journal article [Jang and others, 2018].

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 27-May-2015 (process 1 of 7)
    Deployment sample collection: All specimens were collected from the working half of split cores collected from 201500518 – 20150527. Specimens were stored in heat-sealed plastic specimen bags and refrigerated during the expedition. Depth below sea floor was determined from centimeter scales running alongside the cores during processing, then tied to the continuous downhole depth log using both the IODP standard depth terminologies, which are each based on drilling records of the drill pipe length: CSF-A (total depth from sea floor to target sediment, with any gas expansion gaps included in the depth), CSF-B (total depth from sea floor to target sediment, after all gas expansion gaps have been removed). The sea floor depth reference (mudline) was determined from a combination of noting when the drill string contacted the sea floor and increased the measured weight-on-bit, and visual verification of the drill bit position using an ROV. Person who carried out this activity:
    U.S. Geological Survey
    Attn: William F. Waite
    Research Geophysicist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2346 (voice)
    wwaite@usgs.gov
    Date: 2017 (process 2 of 7)
    Laboratory sampling: After the shipboard specimen collection, the specimens were shipped in coolers with cold packs (nominally at refrigerated, not frozen, temperatures) to the Woods Hole Coastal and Marine Science Center (WHCMSC), where they were subsampled for the sediment settling tests. Person who carried out this activity:
    U.S. Geological Survey
    Attn: William F. Waite
    Research Geophysicist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2346 (voice)
    wwaite@usgs.gov
    Date: 2017 (process 3 of 7)
    Specimen set-up: After oven-drying one of the seven sediment types, sediment was spooned into a 25.4 mm diameter acrylic settling tube (settling tube pictured in the landing page browse graphic). Gentle pluviation of the sediment into the settling tube using the spoon created a loose-packed (maximum void ratio) fabric with a sediment height of 25.4 mm. The sediment was then mixed with a one of the test fluids to a final height of 152.4 mm to obtain a ratio of one to six in the diameter to height of the fluid column. The mixture was allowed to stabilize for more than twelve hours before the cylinder was evacuated in order to remove gas from the fluid. After degassing the fluid, the headspace was reopened to the atmosphere momentarily before a new stopper was inserted into the cylinder top to seal the specimen and water for the duration of the test. The sealed cylinder was shaken for one minute before being left to settle undisturbed. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Junbong Jang
    Geophysicist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2278 (voice)
    508-457-2310 (FAX)
    jjang@usgs.gov
    Date: 2017 (process 4 of 7)
    Measurement: Heights of the depositional interface and the accumulated sediment interface were measured as functions of time until the interface locations stabilized (one to four days, see browse graphic for example of sedimentation behavior). Measurement intervals increased with time in an approximately logarithmic fashion over the course of a complete test to capture time-varying behavior of the sedimentation. Time measurements were made with a stopwatch, and had a precision of ± 0.2 min. Height measurements were made with a ruler affixed to the cylinder, and had a precision of ± 0.1 mm. At the end of each test, the final interface heights were recorded. Graphically, the time required to reach halfway between the initial and final interface heights was recorded as t50 in minutes. The final interface heights were normalized by dividing the interface height by the initial specimen height (25.4 mm). See browse graphic for plotted results. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Junbong Jang
    Geophysicist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2278 (voice)
    508-457-2310 (FAX)
    jjang@usgs.gov
    Date: 2017 (process 5 of 7)
    Fluid preparation: Each specimen was tested in more than one fluid. When the original marine sediment was dried, salt from the in situ pore-fluid precipitated as a solid material. Thus, the initial laboratory mixture of dry sediment with deionized water contained dissolved salt from the in situ pore water, and was identified as a “deionized water with salt” sample (DWS). In order to reduce the effect of salt, approximately 80% of the supernatant fluid in the cylinder was removed after the initial sedimentation test. The cylinder was refilled with deionized water, so the mixture contained freshened water and was identified as a “deionized water, freshened” sample (DWF). The sedimentation test was repeated with the freshened water mixture. Separately, subsamples of the original marine sediment were dried and tested with their in situ salts, using a 2M-brine solution (2M-brine = 2 Molar brine = 2 moles of NaCl in 1 liter of water) and kerosene. Sediment mixtures with 2M-brine and kerosene were not recycled in the sedimentation tests. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Junbong Jang
    Geophysicist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2278 (voice)
    508-457-2310 (FAX)
    jjang@usgs.gov
    Date: 2017 (process 6 of 7)
    Data archiving: Microsoft Excel version 15.33 was used to consolidate all data in a spreadsheet. Measured interface heights and elapsed times were arranged by sediment and pore fluid type. Results were then exported to a comma-separated values (csv) file format. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Junbong Jang
    Geophysicist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2278 (voice)
    508-457-2310 (FAX)
    jjang@usgs.gov
    Date: 07-Aug-2020 (process 7 of 7)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
    Horizontal position was determined by GPS satellite data, which provided guidance information for the dynamic positioning system (DPS) utilized by the D/V Chikyu. The DPS also utilizes inputs from tidal, wind and wave data to control six azimuthal thrusters beneath the hull of the ship. The thrusters are capable of 360 degree adjustment. Given the DPS capabilities, borehole locations for the D/V Chikyu are considered to be accurate to a radius of 15 meters. Details are provided in: Chikyu Hakken - Earth Discovery, Volume 1, Spring 2005, published by JAMSTEC’s Center for Deep Earth Exploration: https://www.jamstec.go.jp/chikyu/e/magazine/backnum/pdf/hk_01_e.pdf
  3. How accurate are the heights or depths?
    Coring depth measurements used on the D/V Chikyu during NGHP-02 followed standard International Ocean Drilling Program (IODP) protocols. Assessment of these protocols by IODP had determined the vertical position accuracy is on the order of centimeters to meters. Additional information about the depth conventions and accuracy are on pages 8 and 9 of the IODP report “IODP Depth Scales Terminology”: http://www.iodp.org/policies-and-guidelines/142-iodp-depth-scales-terminology-april-2011/file. The depth resolution ranges from 0.01 to 1 meter.
  4. Where are the gaps in the data? What is missing?
    As a general rule, only one of the two interfaces could be tracked for an entire test, to havine a T50 time that describes how long it takes for the interface to reach halfway to its final height tends to make sense only for one interface per test. Which interface that is strongly depends on the specimena nd the pore fluid. As an example, only one specimen had a depositional interface in freshened water that could be resolved for the entire test, so there is only one entry for that column. For 2M-Brine and Kerosene, the accumulation interfaces could never be observed for the entire test, so there are no columns for accumulation interfaces for those two fluids. The normalized height columns always refer back to the same interface used for the T50 calculation, so the pattern of blanks for T50 and for the normalized heights is the same. Unless otherwise stated in the column descriptions, blank interface height entries within a column of measured data occur for one of two reasons: either the interface height in question could not be resolved at the stated measurement time, or that particular measurement time was not utilized for the given sediment-fluid pairing.
  5. How consistent are the relationships among the observations, including topology?
    The settlement tubes used in this work were all cut from the same acrylic tube, and thus are all nominally the same diameter. Equal heights of sediment and liquid were used in each test, and agitation times prior to allowing the system to settle were equivalent. This dataset covers the characteristic time and interface heights for each experiment listed here. A second dataset in this data release (Sedimentation Rate Dependence on Pore Fluid Chemistry for Sediment Collected From Area B, Krishna-Godavari Basin, During India's National Gas Hydrate Program Expedition NGHP-02) provides the point-by point measurements over time for each experiment. Consequently, the process steps and many of the spreadsheet columns are the same in the metadata descriptions of the two datasets.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None.
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? This dataset contains four files: NGHP02_AreaB_T50_FinalInterfaceHeight_Data.xlsx (data in an Excel spreadsheet), NGHP02_AreaB_T50_FinalInterfaceHeight_Data.csv (same data in a comma-separated text file), NGHP02_AreaB_T50_FinalInterfaceHeight_BrowseGraphic.png (browse graphic), and FGDC CSDGM metadata in XML format.
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data are available in XLSX and CSV formats, and a browse graphic in PNG format. The user must have software capable of reading the data formats.

Who wrote the metadata?

Dates:
Last modified: 07-Aug-2020
Metadata author:
U.S. Geological Survey
Attn: William F. Waite
Geophysicist
384 Woods Hole Rd.
Woods Hole, MA

508-548-8700 x2346 (voice)
508-457-2310 (FAX)
wwaite@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P9FXJ1VX/NGHP02_AreaB_T50_FinalInterfaceHeight_Metadata.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:19:01 2021