308
K. Leyrer· C. Strohmenger . K. Rockenbauch . T. Bechstaedt
The Al represents the first evaporite member in the succession of Upper Permian sediments in northern Central Europe and, due to its ability to build up
maximum thicknesses of about 300 m, it was able to develop a distinct morphology characterized by a transition from platform to slope and basin depositional
environments (Fig. 4). This transition is characterized by decreasing sediment
thickness from platform (250-300 m) to basin (about 50 m) and by changing
sedimentary structures. Anhydrites in platform position often show salina(swallow-tail anhydrite), and sabkha-type (chicken-wire anhydrite) textures.
Although the Al anhydrite presumably was deposited mainly within water
depths of a few centimeters to a few tens of meters, detailed investigations show
that even minor sea-level fluctuations can be recognized in these thick anhydrite
successions. The deeper-marine anhydrites of slope and basin position are
mainly dark-colored and show typical millimeter-laminations (Linien-type
anhydrite). In platform-position, the overlying Ca2 shows a variety of different
shallow-water facies types (Fig. 5), but with increasing water depth in upper
parts of the slope the sediment becomes more uniform. The deeper parts of the
slope and also the basin sediments of the Ca2 are composed of millimeter-thick,
rhythmically interbedded carbonates with high organic content, which results in
fine laminations similar to the underlying deeper-water anhydrites of the AI.
The Ca2-sealing anhydrites (A2, or Basal Anhydrite) of the second Zechstein cycle reach a maximum thickness of about 60 m on the Ca2-platform. Due to progradation, the thickness of the A2 sediments reaches its maximum of about 100 m
several hundred meters basinward of the Ca2 platform edge and decreases in a
basinward position to less than 5 m.
Sediments younger than the A2 do not influence this simulation study, and
are not described in detail. An overview of the Upper Permian lithostratigraphy
is shown in Fig. 1.
Although our understanding of the Ca2 has improved in recent years, many
important issues like the quantification of sedimentation-controlling parameters and their relative impact on sedimentation during Ca2 time are not completely understood. Additional problems arise when comparing the Ca2 sediments at different locations along the southern margin of the Southern Permian
Basin. Comparisons of Ca2 core data from Northwest German exploration areas
(e.g. South Oldenburg) with data from the East German Ca2-wells in the area of
Southeast Brandenburg show significant differences in sedimentary history.
These differences affect the topographic settings (Fig. 4, 6, 7), the (vertical)
facies patterns, and the thicknesses of different facies members. Because these
differences determine the spatial distribution of potential hydrocarbon reservoir facies, they have to be taken into account to optimize prediction of hydrocarbon reservoirs. High-resolution forward stratigraphic modeling is one of the
most suitable procedures for understanding these differences, and their impact
on sedimentation (Leyrer et al. 1995, 1996).
This chapter shows the results of 2-D forward stratigraphic modeling of the
Ca2 in two different gas-producing areas (South Oldenburg area, Northwest
Germany, and Southeast Brandenburg area, East Germany).
K. Leyrer· C. Strohmenger . K. Rockenbauch . T. Bechstaedt
The Al represents the first evaporite member in the succession of Upper Permian sediments in northern Central Europe and, due to its ability to build up
maximum thicknesses of about 300 m, it was able to develop a distinct morphology characterized by a transition from platform to slope and basin depositional
environments (Fig. 4). This transition is characterized by decreasing sediment
thickness from platform (250-300 m) to basin (about 50 m) and by changing
sedimentary structures. Anhydrites in platform position often show salina(swallow-tail anhydrite), and sabkha-type (chicken-wire anhydrite) textures.
Although the Al anhydrite presumably was deposited mainly within water
depths of a few centimeters to a few tens of meters, detailed investigations show
that even minor sea-level fluctuations can be recognized in these thick anhydrite
successions. The deeper-marine anhydrites of slope and basin position are
mainly dark-colored and show typical millimeter-laminations (Linien-type
anhydrite). In platform-position, the overlying Ca2 shows a variety of different
shallow-water facies types (Fig. 5), but with increasing water depth in upper
parts of the slope the sediment becomes more uniform. The deeper parts of the
slope and also the basin sediments of the Ca2 are composed of millimeter-thick,
rhythmically interbedded carbonates with high organic content, which results in
fine laminations similar to the underlying deeper-water anhydrites of the AI.
The Ca2-sealing anhydrites (A2, or Basal Anhydrite) of the second Zechstein cycle reach a maximum thickness of about 60 m on the Ca2-platform. Due to progradation, the thickness of the A2 sediments reaches its maximum of about 100 m
several hundred meters basinward of the Ca2 platform edge and decreases in a
basinward position to less than 5 m.
Sediments younger than the A2 do not influence this simulation study, and
are not described in detail. An overview of the Upper Permian lithostratigraphy
is shown in Fig. 1.
Although our understanding of the Ca2 has improved in recent years, many
important issues like the quantification of sedimentation-controlling parameters and their relative impact on sedimentation during Ca2 time are not completely understood. Additional problems arise when comparing the Ca2 sediments at different locations along the southern margin of the Southern Permian
Basin. Comparisons of Ca2 core data from Northwest German exploration areas
(e.g. South Oldenburg) with data from the East German Ca2-wells in the area of
Southeast Brandenburg show significant differences in sedimentary history.
These differences affect the topographic settings (Fig. 4, 6, 7), the (vertical)
facies patterns, and the thicknesses of different facies members. Because these
differences determine the spatial distribution of potential hydrocarbon reservoir facies, they have to be taken into account to optimize prediction of hydrocarbon reservoirs. High-resolution forward stratigraphic modeling is one of the
most suitable procedures for understanding these differences, and their impact
on sedimentation (Leyrer et al. 1995, 1996).
This chapter shows the results of 2-D forward stratigraphic modeling of the
Ca2 in two different gas-producing areas (South Oldenburg area, Northwest
Germany, and Southeast Brandenburg area, East Germany).