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Abstract: Revitalizing Mature Miocene Reservoirs in NE Anzoategui: A Sequence Stratigraphic Perspective in the Quiamare and La Celba Oil Fields

Sebastian Galeazzi, Sergio Paredes, Daniel Dellape, Guillermo Moroder

A large proportion of the oil reserves discovered in NE Anzoategui are contained in the 3000-m-thick Lower to Middle Miocene strata of the Oficina Formation. Light oil and gas are contained in multiple sandstone reservoirs. Most producing zones are isolated by shale separators, and feature independent fluid contacts. Individual producing zones are laterally extensive, but locally they show interruptions and considerable internal heterogeneity. Reservoir compartmentalization is due to second or third order accommodation faulting and stratigraphic terminations. Sandstones yielding commercial production range in thicknesses from 10 to 50 ft, and contain intergranular porosities that vary from 6 to 24%. Conjugate-type subvertical fractures locally provide the difference betwe n commercial and non-commercial flow rates in low porosity sandstones. Typically, drive style varies from dissolved gas drive and gas cap expansion to natural water drive where unaltered oil coexists with meteoric water.

The Miocene series are widespread deposits represented by two major transgressive-regressive genetic packages. Observation of facies, parasequence stacking and stratal termination patterns suggests the presence of at least ten depositional sequences. Strata patterns, lithologic and paleontologic criteria indicate that sedimentation took place within a low relief (ramp-type) depositional setting, in depositional environments ranging from coastal plain through estuarine and shallow marine. Individual producing zones represent a variety of systems tracts, which include transgressive systems tracts, lowstand prograding complexes, and less commonly incised valley fill and highstand deposits.

A sequence stratigraphic analysis of the reservoirs in the mature Quiamare oil field has led to the delineation and development of important additional shallow reserves.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela