PATINO-RUIZ, J., and J.R. ROMAN-RAMOS , Pemex Exploration and Production, Northern Region, Mexico

The Tuxpan platform is a Middle Cretaceous reef complex built on a basement high, which bordered the Gulf of Mexico basin during the Late Jurassic. Since 1996, offshore exploration of the Tuxpan platform has been accomplished by the Petroleum System method. This approach has included seismic interpretation, analysis of wells, petrographical and petrophysical studies of reservoir rocks, geochemical analysis of oils and 2D modeling of hydrocarbon generation and migration.

The interpretation of 110 seismic lines allowed identifying the reef facies: lagoon, reef crest and talus. The petrologic and diagenetic studies help to understand the evolution of reservoir porosity, which was linked to eustatic changes. These changes have caused reef crest exposition, infiltration of meteoric water and karstification during Paleogene. The Neogene shaly siliciclastic overburden formed fractures in the reef, enhancing its porosity and permeability. The 2-km thick section of tertiary rocks make up the regional seal.

The biomarker and isotopic results of oils suggest the presence of two genetic families. One family is related to the Upper Jurassic marine shaly limestones and the other one is associated to the Tertiary marine siliciclastic shales. The age of this second genetic family was defined by the presence of Oleanane, which along with the low abundance of homohopanes also indicates that the source is rich in higher plant debris and contains Type 11-111 kerogen deposited in a sub-anoxic shaly environment. The modeling suggests that hydrocarbon generation from Upper Jurassic sources began since the Pliocene. The migration occurs from east to west along carrier beds, unconformity and fault planes.

The teamwork concluded that oil fields have considerable growth potential, that must be determined by reservoir characterization studies, as those that led to additional reserves in two fields, located in the central part of the platform.

AAPG Search and Discovery Article #90908©2000 GCAGS, Houston, Texas