EVIDENCE OF GAS HYDRATE FROM UBGH2 LOG DATA IN THE … · EVIDENCE OF GAS HYDRATE FROM UBGH2 LOG...
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EVIDENCE OF GAS HYDRATE FROM UBGH2 LOG DATA IN THE ULLEUNG BASIN, EAST SEA Gil Young Kim 1 , Dong Geun Yoo 1 , Byong Jae Ryu 1 , Timothy Collett 2 , Michael Riedel 3 , Joon Young Kwak 4 , the UBGH2 Scientists Korea Institute of Geoscience and Mineral Resources, Daejeon, South Korea 1 US Geological Survey, Denver, CO, USA 2 , Geological Survey of Canada, Sidney, BC, Canada 3 Gas Hydrate Research and Development Organization 4 ABSTRACT The Gas Hydrate Research and Development Organization(GHDO) of Korea accomplished successfully the Korea Gas Hydrate Expedition 2010 in the Ulleung Basin(UBGH2), both coring (hydraulic piston and pressure coring) and logging(LWD: logging while drilling and WL: wireline logging), in order to investigate the distribution pattern of gas hydrate in the Ulleung Basin, the East Sea of Korea. The LWD data from 13 sites were obtained and most of the sites showed realistic log data indicating the presence of gas hydrate. In particular, the sites characterized by chimney structure showed extremely high resistivity and velocity relative to normal marine sediments. This suggests that massive hydrates exist into the sediment. The wireline logging(WL) for two sites was also performed. There are good correlations between LWD and WL data. Based on log data, the gas hydrate of the Ulleung Basin likely shows various occurring patterns such as vein/fracture filling type, strata-bound type, pore filling type, and massive type. This was directly identified from some evidence of dissociated hydrates and various hydrate samples collected from coring after LWD. LWD data also strongly support the interpretation for the seismic indicators (e.g., vent or chimney structures, strong BSR, acoustic blanking, enhanced reflection etc) which imply the probability of hydrate presence. Keywords: gas hydrates, log data, Ulleung Basin, East Sea Corresponding author: Phone: +82 42 868 3166 Fax +82 42 868 3166 E-mail: [email protected] INTRODUCTION The physical properties of gas hydrate-bearing sediments help to understand the interaction between gas hydrate and host sediments. Especially, the acoustic velocity dramatically change as gas hydrate concentration, and this relationship may allow remote identification and even quantification of hydrate[1]. In addition, the electrical resistivity is also increased due to the presence of gas hydrate. The Gas Hydrate Research and Development Organization(GHDO) of Korea accomplished UBGH2 as succeeding program of UBGH1 expedition. This paper presents preliminary results of log data acquired from UBGH2 expedition. GEOLOGICAL SETTING The East/Japan Sea(Fig. 1) is a back-arc basin between the eastern margin of the Eurasian plate and the Philippine Sea and Pacific-Okhotsk plates. The opening of the East/Japan Sea was continued from early Oligocene to late Oligocene[2]. The Ulleung Basin is a bowl-shaped back-arc basin. The basin is bounded by steep slope of the Korean Peninsula to the west and by the rugged Korea Plateau to the north. The southern and eastern slopes are relatively gentle. The central part of the basin is underlain by an undeformed sedimentary section up to 5 km thick, while the acoustic basement in the southern basin lies below about 10 km. The acoustic basement consists largely of volcanic materials and is overlain by thick layers Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011 ), Edinburgh, Scotland, United Kingdom, July 17-21, 2011.
Transcript of EVIDENCE OF GAS HYDRATE FROM UBGH2 LOG DATA IN THE … · EVIDENCE OF GAS HYDRATE FROM UBGH2 LOG...
EVIDENCE OF GAS HYDRATE FROM UBGH2 LOG DATA IN THE ULLEUNG BASIN, EAST SEA
Gil Young Kim1 , Dong Geun Yoo1, Byong Jae Ryu1, Timothy Collett2, Michael Riedel3, Joon Young Kwak4, the UBGH2 Scientists
Korea Institute of Geoscience and Mineral Resources, Daejeon, South Korea1
US Geological Survey, Denver, CO, USA2 , Geological Survey of Canada, Sidney, BC, Canada3
Gas Hydrate Research and Development Organization4
ABSTRACTThe Gas Hydrate Research and Development Organization(GHDO) of Korea accomplished successfully the Korea Gas Hydrate Expedition 2010 in the Ulleung Basin(UBGH2), both coring (hydraulic piston and pressure coring) and logging(LWD: logging while drilling and WL: wireline logging), in order to
investigate the distribution pattern of gas hydrate in the Ulleung Basin, the East Sea of Korea. The LWD data from 13 sites were obtained and most of the sites showed realistic log data indicating the presence of gas hydrate. In particular, the sites characterized by chimney structure showed extremely high resistivity and velocity relative to normal marine sediments. This suggests that massive hydrates exist into the sediment. The wireline logging(WL) for two sites was also performed. There are good correlations between LWD and WL data. Based on log data, the gas hydrate of the Ulleung Basin likely shows various occurring
patterns such as vein/fracture filling type, strata-bound type, pore filling type, and massive type. This was directly identified from some evidence of dissociated hydrates and various hydrate samples collected from coring after LWD. LWD data also strongly support the interpretation for the seismic indicators (e.g., vent or chimney structures, strong BSR, acoustic blanking, enhanced reflection etc) which imply the probabilityof hydrate presence.
Keywords: gas hydrates, log data, Ulleung Basin, East Sea
Corresponding author: Phone: +82 42 868 3166 Fax +82 42 868 3166 E-mail: [email protected]
INTRODUCTIONThe physical properties of gas hydrate-bearing sediments help to understand the interaction
between gas hydrate and host sediments. Especially, the acoustic velocity dramatically change as gas hydrate concentration, and this relationship may allow remote identification and even quantification of hydrate[1]. In addition, the electrical resistivity is also increased due to the
presence of gas hydrate. The Gas Hydrate Research and Development Organization(GHDO) of Korea accomplished UBGH2 as succeedingprogram of UBGH1 expedition. This paper presents preliminary results of log data acquired from UBGH2 expedition.
G EOLOGICAL SETTINGThe East/Japan Sea(Fig. 1) is a back-arc basin between the eastern margin of the Eurasian plate
and the Philippine Sea and Pacific-Okhotsk plates. The opening of the East/Japan Sea was continued from early Oligocene to late Oligocene[2]. The Ulleung Basin is a bowl-shaped back-arc basin. The basin is bounded by steep slope of the Korean Peninsula to the west and by the rugged Korea
Plateau to the north. The southern and eastern slopes are relatively gentle. The central part of the basin is underlain by an undeformed sedimentary section up to 5 km thick, while the acoustic basement in the southern basin lies below about 10 km. The acoustic basement consists largely of
volcanic materials and is overlain by thick layers
Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011),Edinburgh, Scotland, United Kingdom, July 17-21, 2011.
of volcanic sill/flow sediment complexes in thenorthern basin[3][4]. Water depths of the Ulleung Basin range from less than 1,000 m in the south margin to over 2,300 m in the northern central basin.
Figure 1. Physiographic map around East/Japan Sea. The marked box is the study area (Ulleung Basin).
SELEC TION OF LOGGING SITESThe logged sites were selected based on seismic indicators(Fig. 2) elucidated through interpretation of seismic data acquired from the Ulleung Basin. The sesimic indicators[5] are characterized by seismic chimney, acoustic blanking, and enhanced reflection, caused by free gas and/or gas hydrate.
The BSR(Bottom Simulating Reflector) is well found. The seismic characteristics of the study area are probably good indicators of gas hydrate presence.
Figure 2. The example of seismic indicators acquired from the study area.
DATA ACQUISITIO NLWD(Schlumberger) and WL(FAOL: Fugro Alluvial Offshore Limited) were conducted at 13 sites and 2 sites, respectively (Figures 3 and 4). The acquired log data are the parameters such as natural gamma, electrical resistivity, acoustic
velocity, neutron porosity, and density. The logged depths range from 280 to 380 m below seafloor.
Figure 3. Schlumberger’s LWD tools deployed for UBGH2 expedition.
Figure 4. Fugro’s WL tools deployed for UBGH2 expedition.
RESULTS AND DISCUSSIONIn this paper, we only present preliminary results(Figs. 5 and 6) acquired during UBGH2 expedition. As shown in the Figure 5, electrical
resistivities show high value (∼ 1000 ohm-m)
compared to unconsolidated marine sediments. This is strongly to suggest the presence of gas hydrate. Generally, the electrical resistivity for
unconsolidated marine sediments is less than 1.0ohm-m, except for sediment layer including carbonate nodules and/or opal diagenesis (Opal-A/Opal-CT boundary)[6]. Kim et al.[7][8][9] have
been reported evidence of gas hydrate using log data acquired from the Ulleung Basin during UBGH1.
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Figure 5. Electrical resistivity from UBGH2. For
comparison, resistivity of Site 797 (ODP Legs127/128) is plotted.
The velocities of UBGH2 generally increase with sediment depth(Figure 6). However, the values show the range from 1600 to 2800 m/s in the
upper part of core. These values are very high compared to unconsolidated marine sediments. Thus, this is probably responsible for the occurrence of gas hydrate in the sediments. The values significantly depend on gas hydrate concentration.
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Figure 6. Velocity from UBGH2. For comparison, resistivity of Site 797 (ODP Legs 127/128) is plotted.
The GVR images (Fig. 7) of UBGH2 representthat the occurrences of gas hydrate show various features such as fracture/vein-filling type, strata-bound type, pore-filling type, and massive type. This is directly confirmed from gas hydrate sample by coring[10].
Figure 7. The examples of GVR images from
UBGH2-6 and UBGH2-11. Note that bright color indicates the presence of gas hydrate.
We compared LWD data with WL data for two sites(UBGH2-6 and UBGH2-10). The compared parameters are electrical resistivity and velocity.
And the interval velocity calculated from VSP data is plotted simultaneously(Figs. 7 and 8). Generally, electrical resistivity from WL is higher than that of LWD, but vice versa in gas hydrate-bearing zone.In case of velocity, WL data is higher than that of LWD. That is why the possible dissociation of gas
hydrate during LWD. Overall, the patterns of individual data show good agreements.
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Figure 7. Electrical resistivity and velocity from LWD, WL, and VSP at UBGH 2-6.
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Figure 8. Electrical resistivity and velocity from LWD, WL, and VSP at UBGH 2-10.
In UBGH2 expedition, we found the evidences of gas hydrate occurrence from log data. Based on log data, the gas hydrate-bearing sediments are likely distributed in the Ulleung Basin, East Sea of
Korea. During coring program of UBGH2, the various gas hydrate samples(vein, nodule, and lamina types) were directly collected(Fig. 8). The evidences of dissociated gas hydrate were found during coring. In this paper, we only present the preliminary result from LWD and WL.
Subsequently, further study will be continued.
Figure 9. Gas hydrate samples from UBGH2
expedition.
REFERENCES[1] Chand S, Minshull, TA. Seismic constraints on the effects of gas hydrate on sediment physical properties and fluid flow; a review, Geofluids
2003;3:275-289. [2] Tamaki K, Suyehero K, Allan J, Ingle JC, Jr., Pisciotto K A. Tectonic synthesis and implications of Japan Sea ODP drilling. Proceedings of Ocean Drilling Program, Scientific Results, part 2, Vol.
127/128. College Station, Texas: Ocean Drilling Program, 1992. [3] Chough SK, Marine geology of Korean Seas. IHRD, Boston, 1983.[4] Lee GH, Kim HJ, Suh MC, Hong JK. Crustal structure, volcanism, and opening mode of the
Ulleung Basin, East Sea (Sea of Japan). Tectonophysics 1999;308:503-525.[5]Yoo DG, Kang DH, Koo NH, Kim GY, KimBY, Chung,SH, Kim YJ, Lee HY, Park KP, Lee GH, Park SC. Geophysical evidence for the occurrence of gas hydrate in the Ulleung Basin,
East Sea. Journal of the Geological Society of Korea, 2008:44:645-655.[6] Kim GY, Yoo DG, Lee HY, Lee YJ, Kim DC.The relationship between silica diagenesis and physical properties in the East/Japan Sea: ODP Legs 127/128. Journal of Asian Earth Sciences,
2007:30:448-456.[7] Kim GY, Yoo DG, Ryu BJ. Sound velocity
property of sediment containing gas hydrate in the Ulleung Basin, East Sea. Journal of Acoustical Society of Korea, 2009:5:424-431[8] Kim GY, Yoo DG, Ryu BJ. Physical property
interpretation of gas hydrate-bearing sediments using log data in the Ulleung Basin, East Sea.Journal of the Geological Society of Korea, 2010:46:275-290.[9] Kim GY, Yi BY, Yoo DG, Ryu BJ, Riedel M. Evidence of gas hydrate fromdownhole logging
data in the Ulleung Basin, East Sea. Marine and Petroleum Geology http://dx.doi.org/10.1016/j.marpetgeo.2011.01.11.[10] UBGH2 Scientists, 2010, Ulleung Basin Gas Hydrate Drilling Expedition2. Prel. Rept., 710 pp.
