Petroleum Systems of Deep-Water Basins - Gulf Coast Section SEPM

Intimate Relations: Interaction of Tectonics and
Sedimentation in the Formation of Roller-Style Fault
Families and Traps in the Eastern East Venezuela
Basin, Trinidad and Venezuela
Lesli J. Wood
Bureau of Economic Geology
The University of Texas at Austin
Austin, Texas 78713-8924
e-mail: lesli.wood@beg.utexas.edu
Abstract
The hydrocarbon-prolific eastern East Maturin Basin of Trinidad and Venezuela is filled with more than 40,000 ft
of deltaic, fluvial/estuarine and deep marine sands and shales deposited in a rapidly subsiding basin along the triple
junction of the westward-subducting Atlantic plate and the obliquely colliding Caribbean and South American plates.
The basin is characterized by several northwest-southeast-striking roller faults across which the Plio-Pleistocene
expands to the northeast. Several thrust-cored anticlinal ridges trend northeast to southwest, and major hydrocarbon
fields are aligned along them.
The last Cretaceous shelf-break trends east to west and has an important influence on the underlying Miocene
interval, which appears to thicken to the north across this paleogeomorphic feature. Increased thickness of Miocene
shales along the northern margin of the basin results in increased shale diapirism in this same region. Bidirectionally
thickened bow-tie anticlines form, whose crests migrate to the east as they become younger, and associated secondary
roll-over faults emerge. These roll-over faults partition hydrocarbon accumulation within the bow-tie structures. Thinning
of Miocene shales along the southern margin of the eastern East Maturin Basin decreases the influence of
diapirism, resulting in formation of monodirectional thickening of section to the west and thinning to the east. Thus
monoclinal structures contain the majority of structural traps in the footwall of younger roller faults. Shale rollers or
secondary roll-over faults are rare.
Understanding the nature and influence that previous paleogeography can exert on a basin’s structure, migration
pathways, and accommodation distribution can lead to improved predrill and postdrill assessment of hydrocarbon systems
risk.
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