Tectonic Setting of Fluvial Reservoirs
Cenozoic basins in southeast Asia were generated
by tectonism associated with the India-Asia collision
(Tapponier et al. 1986; Fig. 1!.65). These include rift
and transtensional basins in offshore Malaysia, Thailand, Cambodia, Vietnam, and the South China Sea
and some onshore basins in these same countries
[grouped together as the Sundaland rifts by Derksen
and McLean-Hodgson (1988)]. Fluvial-deltaic progradation from adjacent contemporaneous uplifts
provided numerous potential reservoir units, and
offshore exploration is now discovering many important oil and gas fields in these basins (Lee 1982;
Crostella 1983; Roberts 1988; Derksen and McLeanHodgson 1988; Blanche 1990). For example, in
Pattani trough, offshore Thailand, a Tertiary-Quaternary fluvial-deltaic section up to 8 km thick is present
and contains important gas accumulations (Blanche
1990). In the Phitsanulok Basin of central Thailand, 8
m3 xl06 of recoverable oil have been discovered to
date from an 8 km Oligocene-Lower Miocene fluviallacustrine succession (Derksen and McLeanHodgson 1988).
14.3.5 Basins in Continental-Transform Settings
Few producing fluvial reservoirs are located in this
type of tectonic setting. The South Belridge field,
California, is an example. The reservoir is a Pliocene
fluvial-deltaic unit derived from uplifts associated
with the San Andreas fault and trapped in associated
anticlinal structures (Miller et al. 1990).
14.3.6 Rift Basins
Several major fluvial exploration plays occur in rift
basins, including East Shetland Basin and Viking
Graben, North Sea (Triassic-Tertiary; Parsley 1984;
Figs. 1!.44, 11.45), and the geologically very similar
Gippsland Basin, Australia (Late Cretaceous-Tertiary; Rahmanian et al. 1990; Figs. 1!.46-1!.48), as
well as the Rec6ncavo Basin of Brazil (Jurassic-Cretaceous) (Figueiredo et al. 1994).
Triassic rift-fill fluvial sediments host a significant
oil field at Wytch Farm in southern Britain (Dranfield
et al. 1987) and gas off the west coast, at Morecambe
field (Stuart and Cowan 1991; G. Cowan 1993; Meadows and Beach 1993).
The rift basins of Africa, including the Karoo
rifts and those originating during the breakup of
Gondwana in the Mesozoic-Cenozoic, all contain significant fluvial clastic units that have yielded oil and
487
gas, but most of these basins are relatively unexplored and the full potential remains to be determined (Genik 1993; Winn et al. 1993; Derksen and
McLean-Hodgson 1988).
14.3.7 Basins on Extensional Continental Margins
Fluvial reservoirs are very important in some extensional, craton-margin basins. The Gulf Coast of the
United States (Fig. 1!.42) is among the most wellknown of such basins, as it has produced huge
volumes of oil and gas from terrigenous clastic reservoirs (Tyler et al. 1984). Most of the reservoirs are
marine in origin, but significant production has
also been obtained from fluvial units forming part
of inland alluvial systems or delta plaius distant
from the coast. Nonmarine stratigraphic units include parts of the Denkman Sandstone (Upper jurassic), Travis Peak Formation (Lower Cretaceous),
Woodbine-Tuscaloosa Formation (Upper Cretaceous), the Wilcox Group (Paleocene-Eocene), and
the Frio Formation (Oligocene).
The Triassic-Tertiary extensional continental
mf:!.rgins of western and northwestern Australia
have yielded significant gas production from fluvial
reservoirs (e.g., Rankin field: Beston 1986; Posaner
and Goldthorpe 1986; Warris 1988).
The Upper Paleozoic to Triassic reservoirs of the
North Slope of Alaska were deposited on the southfacing margins of a craton that was rifted and dispersed during the Cretaceous when the Arctic
Ocean basin was generated (Morgridge and Smith
1972). Other important extensional-margin basins
occur in North Africa (Sirte Basin, of Cretaceous
age, and Cambrian Oued Mya Basin; e.g., Clifford et
al. 1980).
14.3.8 Intracratonic Basins
Intracratonic basins do not constitute a major class
of basin from the point of view of nonmarine petroleum fields, but a few significant discoveries have
been made in this setting. The Morrow Sandstone
(Mississipian) of eastern Colorado and western
Kansas produces from paleovalleys crossing an
intracratonic basin at the margin of the Anadarko
basin. The valleys were incised during glacioeustatic falls in sea level. The Clifford-Siaana trend
in eastern Colorado, which is still undergoing active exploration, is estimated to contain up to
9.5 m3 x 106 of recoverable oil (Bowen et al. 1993).
Cenozoic basins in southeast Asia were generated
by tectonism associated with the India-Asia collision
(Tapponier et al. 1986; Fig. 1!.65). These include rift
and transtensional basins in offshore Malaysia, Thailand, Cambodia, Vietnam, and the South China Sea
and some onshore basins in these same countries
[grouped together as the Sundaland rifts by Derksen
and McLean-Hodgson (1988)]. Fluvial-deltaic progradation from adjacent contemporaneous uplifts
provided numerous potential reservoir units, and
offshore exploration is now discovering many important oil and gas fields in these basins (Lee 1982;
Crostella 1983; Roberts 1988; Derksen and McLeanHodgson 1988; Blanche 1990). For example, in
Pattani trough, offshore Thailand, a Tertiary-Quaternary fluvial-deltaic section up to 8 km thick is present
and contains important gas accumulations (Blanche
1990). In the Phitsanulok Basin of central Thailand, 8
m3 xl06 of recoverable oil have been discovered to
date from an 8 km Oligocene-Lower Miocene fluviallacustrine succession (Derksen and McLeanHodgson 1988).
14.3.5 Basins in Continental-Transform Settings
Few producing fluvial reservoirs are located in this
type of tectonic setting. The South Belridge field,
California, is an example. The reservoir is a Pliocene
fluvial-deltaic unit derived from uplifts associated
with the San Andreas fault and trapped in associated
anticlinal structures (Miller et al. 1990).
14.3.6 Rift Basins
Several major fluvial exploration plays occur in rift
basins, including East Shetland Basin and Viking
Graben, North Sea (Triassic-Tertiary; Parsley 1984;
Figs. 1!.44, 11.45), and the geologically very similar
Gippsland Basin, Australia (Late Cretaceous-Tertiary; Rahmanian et al. 1990; Figs. 1!.46-1!.48), as
well as the Rec6ncavo Basin of Brazil (Jurassic-Cretaceous) (Figueiredo et al. 1994).
Triassic rift-fill fluvial sediments host a significant
oil field at Wytch Farm in southern Britain (Dranfield
et al. 1987) and gas off the west coast, at Morecambe
field (Stuart and Cowan 1991; G. Cowan 1993; Meadows and Beach 1993).
The rift basins of Africa, including the Karoo
rifts and those originating during the breakup of
Gondwana in the Mesozoic-Cenozoic, all contain significant fluvial clastic units that have yielded oil and
487
gas, but most of these basins are relatively unexplored and the full potential remains to be determined (Genik 1993; Winn et al. 1993; Derksen and
McLean-Hodgson 1988).
14.3.7 Basins on Extensional Continental Margins
Fluvial reservoirs are very important in some extensional, craton-margin basins. The Gulf Coast of the
United States (Fig. 1!.42) is among the most wellknown of such basins, as it has produced huge
volumes of oil and gas from terrigenous clastic reservoirs (Tyler et al. 1984). Most of the reservoirs are
marine in origin, but significant production has
also been obtained from fluvial units forming part
of inland alluvial systems or delta plaius distant
from the coast. Nonmarine stratigraphic units include parts of the Denkman Sandstone (Upper jurassic), Travis Peak Formation (Lower Cretaceous),
Woodbine-Tuscaloosa Formation (Upper Cretaceous), the Wilcox Group (Paleocene-Eocene), and
the Frio Formation (Oligocene).
The Triassic-Tertiary extensional continental
mf:!.rgins of western and northwestern Australia
have yielded significant gas production from fluvial
reservoirs (e.g., Rankin field: Beston 1986; Posaner
and Goldthorpe 1986; Warris 1988).
The Upper Paleozoic to Triassic reservoirs of the
North Slope of Alaska were deposited on the southfacing margins of a craton that was rifted and dispersed during the Cretaceous when the Arctic
Ocean basin was generated (Morgridge and Smith
1972). Other important extensional-margin basins
occur in North Africa (Sirte Basin, of Cretaceous
age, and Cambrian Oued Mya Basin; e.g., Clifford et
al. 1980).
14.3.8 Intracratonic Basins
Intracratonic basins do not constitute a major class
of basin from the point of view of nonmarine petroleum fields, but a few significant discoveries have
been made in this setting. The Morrow Sandstone
(Mississipian) of eastern Colorado and western
Kansas produces from paleovalleys crossing an
intracratonic basin at the margin of the Anadarko
basin. The valleys were incised during glacioeustatic falls in sea level. The Clifford-Siaana trend
in eastern Colorado, which is still undergoing active exploration, is estimated to contain up to
9.5 m3 x 106 of recoverable oil (Bowen et al. 1993).