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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Upper Miocene and Pliocene Gas and Oil Plays in the Macuspana Basin, Southeastern Mexico
By
1Bureau of Economic Geology, University of Texas at Austin
2Pemex, México
3Consultant
4University of New Mexico, Department of Earth
and Planetary Sciences
The Bureau of Economic Geology and Pemex Exploración y
Producción conducted an integrated study of the geological,
geochemical and play framework of the upper Miocene and
Pliocene in the Macuspana basin, Mexico, using a variety of well,
core and 2-D and 3-D seismic data (Fig. 1). Structural controls
for the plays consist of deep-seated faults that tap Mesozoic thermogenic
gas sources, areas of intense shale diapirism and folding
and areas with structural inversion that could enhance trapping
and reservoir productivity. Early Neogene thrusting south of the
basin triggered evacuation of Oligocene shale along northwest-dipping
listric faults in the eastern
and southeastern margin of
the basin. These faults are associated
with large-scale rollover
structures and thick (>500 m)
upper Miocene shoreface and
wave-dominated, deltaic complexes.
Traps occur as both
four-way and three-way structural-
stratigraphic combinations.
Reservoir seal
is provided
by a 100- to 300-m lower
Pliocene transgressive shale.
Downdip pinch-out of reservoir-quality shoreface sandstones is
a key risk factor in the upper Miocene in the onshore part of the
basin. In contrast, the offshore, upper Miocene section consists
of deep water slope systems downdip of an inferred clastic-carbonate
source associated with the Yucatán Platform. Thin,
calcareous, turbidite sandstones lapped onto a major turtle
structure, potentially providing updip-porosity pinch-outs.
A second phase of extension in the early Pliocene formed a set
of broad, southeast-dipping listric faults in the western basin,
controlling thick accumulations of stacked Pliocene shoreface
deposits. Sandy Pliocene shoreface depocenters formed in shale-withdrawal
sub-basins, primarily in the northwestern part of the
basin. Trap formation and enhancement in the southern basin
margin are linked to late Miocene-to-Pliocene inversion. Unlike in
the more productive upper Miocene, reservoir seal
is a major risk
factor in upper and middle Pliocene reservoirs having few thick
upper bounding shales
Figure 1. (a) Location of the Macuspana Basin, with structural elements. (b) Well control and distribution of 3-D surveys and principal 2-D seismic lines used in the study.
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Three petroleum systems (Mesozoic, Paleogene/Lower Neogene and Upper Miocene/Pliocene) contributed to the hydrocarbon accumulations and to hydrocarbon generation and migration in the basin. Principal Upper Jurassic/Lower Cretaceous source rocks generated wet thermogenic gases and oil. Secondary, lower Tertiary source rocks generated predominantly dry, biogenic gases. Mixtures of the two gas types are common. Numerous deep-seated growth faults and other faults serve as pathways for Mesozoic-sourced hydrocarbons. Surface seeps and abundant gas shows suggest that hydrocarbons are being generated today.
This study was published in the September 2003 Bulletin of the American Association of Petroleum Geologists (volume 87, number 3, p. 1411–1435). AAPG members can access the text and figures at the AAPG website: http://www.aapg.org/.
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