Escalona, Alejandro¹, Paul Mann¹
(1) Jackson School of Geosciences, The University of Texas at Austin, Austin, TX

ABSTRACT: Regional Tectonics, Stratigraphy, Reservoir Characterization, and Petroleum Systems in an Eocene Foreland Basin, Maracaibo Basin, Venezuela

The 4-km-thick Eocene clastic section of the Maracaibo Basin has produced more that 40 billion bbl of oil since the 1920’s. This study uses well and seismic data to image Eocene rocks in the subsurface of the Maracaibo basin in order to determine the tectonic and eustatic control on shallow marine reservoirs and petroleum systems. The Maracaibo foreland basin was filled by Eocene clastic rocks during the collision between the Caribbean arc system and the passive margin of northern South America. Eocene thrust faulting affected the area east of the present-day Lake Maracaibo. The present-day lake area was affected by flexural faults related to downwarping of the continental crust towards the collisional area and by north-south strike-slip faults following the trend of Late Jurassic rifts. 3D data reveal that flexural and strike-slip faults on the Eocene shelf controlled the distribution of fluvial and tide dominated delta systems. A major angular unconformity spanning the interval from middle Eocene to Oligocene truncates folded and faulted Eocene rocks. This so-called “Eocene unconformity” is interpreted as a rebound effect related to SE migration of post-Eocene thrusting and crust relaxation of the present-day lake area. The Eocene unconformity forms a major seal on hydrocarbons generated by late Cretaceous source rocks during the Paleogene. NS-trending structural highs produced during Eocene provide traps for hydrocarbons moving updip along steep-dipping faults. In some areas, continued displacement on these faults and EW shortening from early Miocene to present time across the lake area allowed hydrocarbons migration into Miocene reservoirs.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.