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Characterization of gas hydrate reservoirs by integration of core and log data in the Ulleung Basin, East Sea

Marine and Petroleum Geology

By:
, , , , , , , ,
DOI: 10.1016/j.marpetgeo.2013.05.007

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Abstract

Examinations of core and well-log data from the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) drill sites suggest that Sites UBGH2-2_2 and UBGH2-6 have relatively good gas hydrate reservoir quality in terms of individual and total cumulative thicknesses of gas-hydrate-bearing sand (HYBS) beds. In both of the sites, core sediments are generally dominated by hemipelagic muds which are intercalated with turbidite sands. The turbidite sands are usually thin-to-medium bedded and mainly consist of well sorted coarse silt to fine sand. Anomalies in infrared core temperatures and porewater chlorinity data and pressure core measurements indicate that “gas hydrate occurrence zones” (GHOZ) are present about 68–155 mbsf at Site UBGH2-2_2 and 110–155 mbsf at Site UBGH2-6. In both the GHOZ, gas hydrates are preferentially associated with many of the turbidite sands as “pore-filling” type hydrates. The HYBS identified in the cores from Site UBGH2-6 are medium-to-thick bedded particularly in the lower part of the GHOZ and well coincident with significant high excursions in all of the resistivity, density, and velocity logs. Gas-hydrate saturations in the HYBS range from 12% to 79% with an average of 52% based on pore-water chlorinity. In contrast, the HYBS from Site UBGH2-2_2 are usually thin-bedded and show poor correlations with both of the resistivity and velocity logs owing to volume averaging effects of the logging tools on the thin HYBS beds. Gas-hydrate saturations in the HYBS range from 15% to 65% with an average of 37% based on pore-water chlorinity. In both of the sites, large fluctuations in biogenic opal contents have significant effects on the sediment physical properties, resulting in limited usage of gamma ray and density logs in discriminating sand reservoirs.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Characterization of gas hydrate reservoirs by integration of core and log data in the Ulleung Basin, East Sea
Series title:
Marine and Petroleum Geology
DOI:
10.1016/j.marpetgeo.2013.05.007
Volume
47
Year Published:
2013
Language:
English
Publisher:
Elsevier
Contributing office(s):
Central Energy Team
Description:
13 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Marine and Petroleum Geology
First page:
30
Last page:
42
Number of Pages:
13
Country:
Korea
Other Geospatial:
East Sea Of Korea;Ulleung Basin