Chapter 15
Case Studies of Oil a11d Gas Fields ill Fluvial Reservoirs
15.1 Introduction
Selected examples of petroleum plays in fluvial sandstones are summarized in Tables 14.3, 14.4. Some of
the major oil fields from these plays are summarized
in Tables 15.1 and 15.2. A large number of additional
fields are described briefly in the literature cited in
Chap. 14 (particularly in the SE Asia and Australia
areas), but reservoir and production data are inadequate for complete tabulation. Gas fields have not
been tabulated for this book. The purpose of this
chapter is to provide a suite of documented case
studies of selected examples of these fields, in order
to illustrate the three main types of reservoir configuration identified in Chap. 14.
15.2 Paleovalley Fields (PV Type)
15.2.1 Little Bow Area, Alberta
The Mannville Sandstone (Lower Cretaceous) is a
fluvial, lacustrine) coastal deltaic and barrier) and
open marine unit that extends throughout central
and southern Alberta. This play is located within the
Alberta Basin, a large foreland basin that extends
throughout Western Canada and was formed by
terrane collision and suturing activity between the
jurassic and the mid-Cenozoic (Sect. 11.4.6). The
Mannville and underlying Jurassic deposits contain
many small oil fields trapped in fluvial and deltaic
channel sandstones in central and southern Alberta.
Many are formed in paleovalleys. Wood and
Hopkins ( 1992) identified eight levels of valley cutand-fill in the Glauconitic Sandstone Member of
the Upper Mannville. The Mannville Sandstone is in
part correlative with the McMurray Formation
(Athabasca Oil Sands) of northern Alberta, the
Cutbank Sandstone of Montana, and the "rand "D"
sandstones of the Denver Basin, all of which contain
similar PV -type fields. The group consists of several
formations and members and contains several internal, regional unconformities. The internal stratigraphy of the unit is very complex, because one or more
of the members have locally been removed by intraMannville erosion. Recognition and correlation of
the· members is difficult, because they are present
only in the subsurface, and detailed stratigraphic
work must rely on precise lithostratigraphic correlation of closely spaced wireline logs and petrographic
analysis of the sandstones. The unit and its component formations/members have been assigned a
large number of alternative local names, reflecting
the fact that much of the outcrop and subsurface
stratigraphic work represents local studies carried
out in isolation from one another. A thorough regional reevaluation of the Mannville incorporating
concepts of sequence stratigraphy still needs to be
carried out {the most recent synthesis is that by
Hayes et al. (1994)].
The Alberta Basin generally is characterized by a
gentle dip to the southwest, toward the fold-thrust
belt of the Rocky Mountains. In the southeast corner
of the province is the buried Sweetgrass Arch; regionally the beds dip to the north and northwest
away from this subtle feature. These dips impose an
overriding structural control on all stratigraphic
traps, in that it is necessary for there to be an updip
seal on the east side of each trap. In most cases in the
Mannville Group, this is provided by the juxtaposition of porous Mannville strata filling a paleovalley
against impermeable beds of the host rocks (generally older Mannville beds).
In southern Alberta (Fig. 15.1) the Glauconitic
Sandstone of the Upper Mannville Group contains
numerous sandstone ribbons that are interpreted as
valley fills (Hopkins et al. 1982; Hopkins 1985).
These rocks exemplify a ·problem common in the
subsurface analysis of fluvial channels associated
with marginal-marine rocks: Are the channels contemporaneous with the host strata1 or are they
younger deposits formed following a period of baselevel lowering and incision? The presence of a deeply
scoured contact between the channel and the host
rocks does not demonstrate that the channels are
Case Studies of Oil a11d Gas Fields ill Fluvial Reservoirs
15.1 Introduction
Selected examples of petroleum plays in fluvial sandstones are summarized in Tables 14.3, 14.4. Some of
the major oil fields from these plays are summarized
in Tables 15.1 and 15.2. A large number of additional
fields are described briefly in the literature cited in
Chap. 14 (particularly in the SE Asia and Australia
areas), but reservoir and production data are inadequate for complete tabulation. Gas fields have not
been tabulated for this book. The purpose of this
chapter is to provide a suite of documented case
studies of selected examples of these fields, in order
to illustrate the three main types of reservoir configuration identified in Chap. 14.
15.2 Paleovalley Fields (PV Type)
15.2.1 Little Bow Area, Alberta
The Mannville Sandstone (Lower Cretaceous) is a
fluvial, lacustrine) coastal deltaic and barrier) and
open marine unit that extends throughout central
and southern Alberta. This play is located within the
Alberta Basin, a large foreland basin that extends
throughout Western Canada and was formed by
terrane collision and suturing activity between the
jurassic and the mid-Cenozoic (Sect. 11.4.6). The
Mannville and underlying Jurassic deposits contain
many small oil fields trapped in fluvial and deltaic
channel sandstones in central and southern Alberta.
Many are formed in paleovalleys. Wood and
Hopkins ( 1992) identified eight levels of valley cutand-fill in the Glauconitic Sandstone Member of
the Upper Mannville. The Mannville Sandstone is in
part correlative with the McMurray Formation
(Athabasca Oil Sands) of northern Alberta, the
Cutbank Sandstone of Montana, and the "rand "D"
sandstones of the Denver Basin, all of which contain
similar PV -type fields. The group consists of several
formations and members and contains several internal, regional unconformities. The internal stratigraphy of the unit is very complex, because one or more
of the members have locally been removed by intraMannville erosion. Recognition and correlation of
the· members is difficult, because they are present
only in the subsurface, and detailed stratigraphic
work must rely on precise lithostratigraphic correlation of closely spaced wireline logs and petrographic
analysis of the sandstones. The unit and its component formations/members have been assigned a
large number of alternative local names, reflecting
the fact that much of the outcrop and subsurface
stratigraphic work represents local studies carried
out in isolation from one another. A thorough regional reevaluation of the Mannville incorporating
concepts of sequence stratigraphy still needs to be
carried out {the most recent synthesis is that by
Hayes et al. (1994)].
The Alberta Basin generally is characterized by a
gentle dip to the southwest, toward the fold-thrust
belt of the Rocky Mountains. In the southeast corner
of the province is the buried Sweetgrass Arch; regionally the beds dip to the north and northwest
away from this subtle feature. These dips impose an
overriding structural control on all stratigraphic
traps, in that it is necessary for there to be an updip
seal on the east side of each trap. In most cases in the
Mannville Group, this is provided by the juxtaposition of porous Mannville strata filling a paleovalley
against impermeable beds of the host rocks (generally older Mannville beds).
In southern Alberta (Fig. 15.1) the Glauconitic
Sandstone of the Upper Mannville Group contains
numerous sandstone ribbons that are interpreted as
valley fills (Hopkins et al. 1982; Hopkins 1985).
These rocks exemplify a ·problem common in the
subsurface analysis of fluvial channels associated
with marginal-marine rocks: Are the channels contemporaneous with the host strata1 or are they
younger deposits formed following a period of baselevel lowering and incision? The presence of a deeply
scoured contact between the channel and the host
rocks does not demonstrate that the channels are