Print this pageUpper Jurassic Source Rocks in Ultra-Deepwaters of the Southern Gulf of Mexico: Implications for Petroleum Systems in Mexico’s Offshore Frontier Areas
Late Triassic to Early Jurassic continental rifting culminated in the opening of the Gulf of Mexico during Middle to early Late Jurassic time. This was followed in the Late Jurassic by a period of tectonic stability and basinal subsidence, along with the accumulation of Kimmeridgian, Oxfordian, and Tithonian successions which have long been recognized as the source rocks for most of the hydrocarbons generated in the Mexican Gulf of Mexico.
In an effort to understand the Mesozoic tectonic evolution, structural setting, depocenter distribution, and thickness of potential Jurassic source rocks in the deep and ultra-deep waters of the Gulf of Mexico, Repsol and Pemex teams mapped, using 2D seismic data, an area of approximately 400,000 km2 between the southern edge of the Sigsbee Escarpment, the westernmost Florida Platform, the northwest margin of the Campeche Escarpment, and east of the Mexican Cordilleras.
This large-scale mapping reveals that the Jurassic has basin-wide distribution across the Gulf of Mexico. The Jurassic section occurs in the following settings: 1) the thickest sedimentary sections accumulated in rift grabens fills within transitional crust and 2) relatively thin sequences overlying what may be oceanic crust, in the abyssal plain. It is noteworthy that Jurassic rocks are absent over relict structural highs associated with Late Triassic-Early Jurassic rifting in the eastern and northeastern parts of the basin, particularly to the west of the Florida platform.
The existence of potential Jurassic source rocks throughout the southern Gulf has profound implications for oil and gas exploration. The very prolific petroliferous Upper Jurassic marine section in the Mexican Gulf of Mexico correlates with Upper Jurassic source rocks in the Florida Straits, and these strata have generated most of the produced hydrocarbons in the region.
The widespread distribution of Upper Jurassic rocks having generative potential, the thick overburden, and the existence of oil seeps in the Sigsbee Knolls area suggest the possible trapping of hydrocarbons along the edge of the Campeche Escarpment, particularly in the trend of contractional structures and associated salt diapirs that intrude Cretaceous fractured basinal carbonates; and in the breccia play at the K/T boundary. Because mature areas occur to the west and north of the southern Gulf margin, southward lateral migration of hydrocarbons may be critical for entrapment in the aforementioned plays.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil