512
88
A311
Fig. 15.18. Conceptual model of the large-scale architecture of the Stat:fjord Formation, Statfjord field. Well spacing is approximately 1 km, The section is oriented
major petroleum plays in this area (Parsley 1984).
Several giant oil fields contain significant reserves in
these fluvial sandstones, including Brent, Snorre,
Ninian, and Statfjord in the north Viking Graben
and Beatrice in the Moray Firth Basin.
The Triassic and Jurassic rocks of the North Sea
were developed during a phase of repeated rift faulting, related to the incipient opening of the Atlantic
Ocean (Ziegler 1988). The Viking-Central Graben
was the major structure to develop at this time (Fig.
11.44). Regional subsidence that accompanied rifting activated regional drainages, leading to the development of major fluvial units, the Cormorant and
Statfjord Formations (Rhaetic-Hettangian) (Fisher
1984). With continued subsidence marine transgression occurred, and the largely delt�ic Brent Group
(Aalenian-Bajocian) was deposited (Brown 1984).
Faulting and folding occurred in mid- to Late Jurassic time, and the fault blocks were tilted, uplifted,
Case Studies of Oil and Gas Fields in Fluvial Reservoirs
A37
A33
c::: :: :: ::=·=·7/
north�south, parallel to assumed drainage direction.
(MacDonald and Halland 1993, reprinted by permission)
and eroded (Figs. 15.15, 15.16). Subsequent Late Jurassic (Kimmeridgian) and Cretaceous transgressions covered the eroded fault blocks with shales,
including the Kimmeridge Shale, a prolific source
rock. The shales also provide the seals for these north
Viking Graben oil fields.
Petroleum occurs in two main fluvial units, the
Statfjord Formation, the sandstones of which are
relatively widely distributed and characterized by
good porosity, and the Brent Group, where this unit
includes sandstones of fluvial, rather than deltaic
origin. The Cormorant Formation typically is thin
and impersistent, and displays poor reservoir characteristics, although it has yielded some oil and gas
shows, notably in the Beryl field (Fisher 1984).
Petroleum occurrences in Triassic� Jurassic strata
of the northern North Sea are trapped in faultbounded anticlinal structures (Fig. 15.17). Stratigraphic trapping mechanisms are secondary. The
88
A311
Fig. 15.18. Conceptual model of the large-scale architecture of the Stat:fjord Formation, Statfjord field. Well spacing is approximately 1 km, The section is oriented
major petroleum plays in this area (Parsley 1984).
Several giant oil fields contain significant reserves in
these fluvial sandstones, including Brent, Snorre,
Ninian, and Statfjord in the north Viking Graben
and Beatrice in the Moray Firth Basin.
The Triassic and Jurassic rocks of the North Sea
were developed during a phase of repeated rift faulting, related to the incipient opening of the Atlantic
Ocean (Ziegler 1988). The Viking-Central Graben
was the major structure to develop at this time (Fig.
11.44). Regional subsidence that accompanied rifting activated regional drainages, leading to the development of major fluvial units, the Cormorant and
Statfjord Formations (Rhaetic-Hettangian) (Fisher
1984). With continued subsidence marine transgression occurred, and the largely delt�ic Brent Group
(Aalenian-Bajocian) was deposited (Brown 1984).
Faulting and folding occurred in mid- to Late Jurassic time, and the fault blocks were tilted, uplifted,
Case Studies of Oil and Gas Fields in Fluvial Reservoirs
A37
A33
c::: :: :: ::=·=·7/
north�south, parallel to assumed drainage direction.
(MacDonald and Halland 1993, reprinted by permission)
and eroded (Figs. 15.15, 15.16). Subsequent Late Jurassic (Kimmeridgian) and Cretaceous transgressions covered the eroded fault blocks with shales,
including the Kimmeridge Shale, a prolific source
rock. The shales also provide the seals for these north
Viking Graben oil fields.
Petroleum occurs in two main fluvial units, the
Statfjord Formation, the sandstones of which are
relatively widely distributed and characterized by
good porosity, and the Brent Group, where this unit
includes sandstones of fluvial, rather than deltaic
origin. The Cormorant Formation typically is thin
and impersistent, and displays poor reservoir characteristics, although it has yielded some oil and gas
shows, notably in the Beryl field (Fisher 1984).
Petroleum occurrences in Triassic� Jurassic strata
of the northern North Sea are trapped in faultbounded anticlinal structures (Fig. 15.17). Stratigraphic trapping mechanisms are secondary. The