Geoscience Reference
In-Depth Information
Table 5. Characteristic features and criteria used in the interpretation of three major luvial channel types in the Lunde
Formation and the Statfjord Group: single, straight or low-sinuous (steer head), high sinuous (meandering), low sinuous
(braided) (see Fig. 3).
Common
thickness
range
Channel
type
Vertical trend and
correlation
Characteristic features and facies
Example
Erosive lower boundary, commonly with
channel base conglomerate with mudstone
clasts. Sharp upper boundary commonly
draped by oodplain mudstone
Bell-shaped to box-shaped
grain-size and gamma ray
trends with sharp base and
top
34/4-C-6 H
Extrabasinal pebbles (quartz, quartzite,
granite) in some stratigraphic intervals
Individual channel units
commonly form multistorey
sandstone bodies
Multistorey channel
sandstone bodies are
commonly correlated
between wells at distances
up to some kilometres
Dominantly plane-parallel and low-angle
cross-stratication, interchanging with
less frequent and thinner beds of trough
cross-stratication
6 to 7 m
Frequent internal erosive surfaces and
cut-and ll structures
Dominant medium sand grain size varies
considerably in sorting within and between
adjacent beds
No to minor internal bioturbation
34/7-P-29
Erosive lower boundary, frequently with
mudstone and calcrete clasts at the base.
The upper boundary is transitional into
overlying oodplain mudstone
Overall upward ning grain-
size trend and gamma ray
values increasing into
background values of
overlying oodplain
mudstone
Clear separation between
RHOB/NPHI curves in
uppermost part of upward
dirtying well log trend
Lower part dominated by thick bedsets
with trough cross-stratication, separated
by slightly inclined accretion surfaces
frequently lined with small mudstone
and calcrete clasts
Upper part dominated by decreasing
dimension of trough cross-stratication,
passing into ripple cross lamination,
accretion surfaces draped with some
cm-thick silt and mudstone beds
Dominant sand grain size from medium to
ne, slight variation in sorting within and
between adjacent beds
8 to 13 m
Individual channel units
form multistorey sandstone
bodies in upper part of the
Lunde Formation
Channel belts above
zonation boundaries are
correlated some kilometres
between wells
Bioturbation common in mudstone beds
in upper part
Erosive lower boundary, commonly
covered with intra-basinal mudstone clasts
Lower part dominated by trough cross-
stratied or plane parallel-stratied
sandstone beds
Distinct single upward fining
and gamma ray trends
Occur as single channel inll
units within mudstone-
dominated stratigraphic
intervals
Channel sandstone units
commonly not correlated
between wells
34/7-P-29
3 to 7 m
Upper part is commonly ripple cross-
laminated
Dominant sand grain size ne to very ne
Bioturbation is abundant, particularly in
upper part
Search WWH ::




Custom Search