--> Abstract: Applied Sequence Stratigraphy of the Oficina Formation, Eastern Basin, Venezuela, by T. B. Berge, J. Delgado, L. Hernabdez, A. Ramos, and E. Roa; #90937 (1998).

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Abstract: Applied Sequence Stratigraphy of the Oficina Formation, Eastern Basin, Venezuela

BERGE, TIMOTHY B., Subsurface Consultants, JOSE DELGADO, LUCINDA HERNANDEZ, ALBERTO RAMOS, and ELIAS ROA, Corpoven S.A.

The Eastern Basin has a tectonic history of transition ( at about 25.5 Mybp) from a passive margin to a foreland basin. Periods of extension (16 to 9.2 Mybp) and compression (9.2 Mybp to recent) during the development of the foreland and a shift in the depocenter position from north during the Oligocene to the east by the late Miocene is the result of lithospheric flexure of the South American plate caused by the progressive eastward impingement of the Caribbean Plate.

The Oficina is a clastic unit that was deposited on a broad marginal shelf into the developing foredeep to the north. The unit consists of five 3d-order depositional sequences with boundaries at 25.5, 22, 17.5, 16.5, 15.5 and 10.5 Mybp. These were deposited during a regressive 2nd-order phase that culminated with a flooding event in the middle Freites above the Oficina at about 9.2 Mybp. These have been established by interpretation of stratal geometries, primary depositional features and parasequence stacking patterns using seismic , well logs , core and biostratigraphic information.

One exciting finding of this study is the identification of a lowstand wedge play at the base of each of three sequences in the lower Oficina ( above SB22, SB17.5, and SB16.5 ). These proven reservoirs have better production characteristics than any of the other intervals in the Oficina and extend the play area into deeper untested areas to the north, whereas the static deltaic paradigm would condem the northern area as reservoir-poor.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah