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ABSTRACT: Sequence Stratigraphic Analysis as an Exploration and Production Tool in the Ceuta Eocene Field, Maracaibo Basin, Venezuela

Rodriguez Argenis

Oil plays in Ceuta field, as in other areas of the Maracaibo Lake, were delineated using the common methodology of standard seismic reflection interpretation. Prospective structures were defined and drilled, and suites of logs were then used for petrophysical evaluation of the section of interest. These established seismic and petrophysical techniques for delineating oil-bearing intervals in the Maracaibo basin failed to perform as expected in Ceuta Eocene. Here, after drilling and coring well VLG-3726 in a prospective structure, it was proven that although logs showed high resistivity in sand intervals with good porosity, it did not necessarily mean commercial hydrocarbon accumulation. To explain this phenomenon, a sequence stratigraphic analysis of the cored 600-ft (200 m) section was done. Results showed that petrophysical evaluation correctly identified sand intervals with good porosity, but in particular instances this porosity was unconnected. For example, sand facies S1 and S2, with good secondary, uneffective porosity was not oil bearing. These facts could explain their sand-log response, high resistivity, and noncommercial oil accumulation. This analysis also explained the role played by depositional and diagenetic processes in delineating sand body geometries and reservoir qualities for proposing an exploration or development program. From this study, I was concluded that application of rock data through a facies analysis subordinates seismic and petrophysical consideration for hydrocarbon evaluation in this and other areas with similar sediment logical characteristics.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990