TY - JOUR
T1 - Chemostratigraphy of upper Jurassic reservoir sandstones, Danish Central Graben, North Sea
AU - Weibel, R.
AU - Johannessen, P.N.
AU - Dybkjær, K.
AU - Rosenberg, P.
AU - Knudsen, C.
PY - 2010/8
Y1 - 2010/8
N2 - A chemostratigraphic study of Upper
Jurassic sandstones in the northern Danish Central Graben has been
undertaken within the framework of a well-defined
stratigraphic/sedimentological model based particularly on cored well
sections. Two reservoir sandstone units are recognised, the
transgressive marginal marine to shoreface sandstone of the Gert Member
and the regressive to transgressive shoreface sandstone of the Ravn
Member. Both members belong to the Heno Formation, which is equivalent
to the Fulmar Formation (UK) and the Ula Formation (Norway).Multivariate
analysis of geochemical data from 264 core samples from 8 wells reveals
the distinction between the two reservoir sandstones (Gert and Ravn
members) and the two offshore claystones (Farsund and Lola formations).
Specific elements have proven to be important for this separation and
these elements demonstrate differences even in 2-dimensional cross
plots. The Farsund Formation is characterised by higher V, U and P2O5, and lower MgO and K2O when compared with the Lola Formation. The Gert Member typically has higher maximum amounts of Cr and TiO2 than the Ravn Member. The high Cr and TiO2
content (probably from chrome spinel and Ti-minerals) might be related
to a source of exposed Carboniferous sediments in the Gert Ridge area.
The Ravn Member is characterised by higher Na2O, P2O5 and Th contents than the Gert Member, which may reflect a higher content of plagioclase (Na2O)
and a changed heavy mineral assemblage. The Mid North Sea High is a
likely source for the heavy mineral suite that characterises the Ravn
Member. The Rita-1 well, situated closest to the Mid North Sea High,
seems to have been more influenced by this source than the other wells.
In the Hejre area, a volcanic source supplying K-feldspar may be
responsible for the relatively high K2O/Al2O3
observed in both the Gert and Ravn members. Hence in addition to
differentiation between the two reservoir sands and between the two
offshore claystones, this study also illustrates the use of geochemical
data for evaluation of source characteristics and dominance of different
sediment source areas.
AB - A chemostratigraphic study of Upper
Jurassic sandstones in the northern Danish Central Graben has been
undertaken within the framework of a well-defined
stratigraphic/sedimentological model based particularly on cored well
sections. Two reservoir sandstone units are recognised, the
transgressive marginal marine to shoreface sandstone of the Gert Member
and the regressive to transgressive shoreface sandstone of the Ravn
Member. Both members belong to the Heno Formation, which is equivalent
to the Fulmar Formation (UK) and the Ula Formation (Norway).Multivariate
analysis of geochemical data from 264 core samples from 8 wells reveals
the distinction between the two reservoir sandstones (Gert and Ravn
members) and the two offshore claystones (Farsund and Lola formations).
Specific elements have proven to be important for this separation and
these elements demonstrate differences even in 2-dimensional cross
plots. The Farsund Formation is characterised by higher V, U and P2O5, and lower MgO and K2O when compared with the Lola Formation. The Gert Member typically has higher maximum amounts of Cr and TiO2 than the Ravn Member. The high Cr and TiO2
content (probably from chrome spinel and Ti-minerals) might be related
to a source of exposed Carboniferous sediments in the Gert Ridge area.
The Ravn Member is characterised by higher Na2O, P2O5 and Th contents than the Gert Member, which may reflect a higher content of plagioclase (Na2O)
and a changed heavy mineral assemblage. The Mid North Sea High is a
likely source for the heavy mineral suite that characterises the Ravn
Member. The Rita-1 well, situated closest to the Mid North Sea High,
seems to have been more influenced by this source than the other wells.
In the Hejre area, a volcanic source supplying K-feldspar may be
responsible for the relatively high K2O/Al2O3
observed in both the Gert and Ravn members. Hence in addition to
differentiation between the two reservoir sands and between the two
offshore claystones, this study also illustrates the use of geochemical
data for evaluation of source characteristics and dominance of different
sediment source areas.
KW - Bulk-rock geochemistry
KW - Chemostratigraphy
KW - Geochemical distinction
KW - Gert Member
KW - Heno Formation
KW - Ravn Member
KW - Reservoir sandstone
KW - Sand provenance
KW - Sediment source area
UR - http://www.scopus.com/inward/record.url?scp=77954657603&partnerID=8YFLogxK
U2 - 10.1016/j.marpetgeo.2010.06.001
DO - 10.1016/j.marpetgeo.2010.06.001
M3 - Article
SN - 0264-8172
VL - 27
SP - 1572
EP - 1594
JO - Marine and Petroleum Geology
JF - Marine and Petroleum Geology
IS - 7
ER -