gas hydrate - CCOP

Figure 1. Coalfields in South Korea
The late Carboniferous to early Triassic Pyeongan Supergroup crops out in the Ogcheon belt
(Figure 1). In the Samcheog Coal Field (SCCF), the largest in South Korea, containing fortyfour
percent of national reserves, the Pyeongan Supergroup was divided by Cheong (1969)
into seven formations; the Manhang, Geumcheon, Jangseong, Hambaegsan, Dosagog, Gohan
and Donggo Formations in ascending order (Figure 2). These mainly consist of sandstone,
shale, coal and some limestone (Figure 3). The detailed lithostratigraphy and depositional
environments of the supergroup have been discussed by Lee & Chough (2006). Up to seven
coal seams are interbedded in the Jangseong and Geumcheon formations. The thickness of
these coal seams varies from 0.6 to 4.0 meters in non-tectonised areas, but local deformation
including folding and thrusting has given rise to local variations of thickness and lateral
continuity. The dips of the coal seam are normally steep, ranging from thirty to eighty degrees.
Surface occurrence of coal seams extends to a maximum of almost 100km in the SCCF. The
rank of coal is classed as anthracite to meta-anthracite.
The late Triassic to early Jurassic Daedong Group, unconformably overlying either
Precambrian gneiss or the Pyeongan Supergroup, occurs in the Ogcheon belt and the
Gyeonggi massif (Figure 1). The so-called Bansong, Nampo and Kimpo Groups are broadly
correlated with the Daedong Group, depending upon the localities of occurrence; however the
precise stratigraphic correlation of the each group is not yet determined. The Daedong Group
mainly consists of conglomerate, sandstone, shale and several horizon of coal. The total
thickness of the sedimentary sequences varies from 400 meters in the case of the Bansong
Group., 1,600 meters for the Kimpo Group and up to 3,000 meters for the Nampo Group
(Reedman and Um 1975). The latter Group includes twenty-five to thirty coal seams in the
Chungnam Coalfield (CNCF, Figure 4)) and id divided into five formations; the Hajo,
New Energy Resources in the CCOP Region - Gas Hydrates and Coalbed Methane 121