Abstract: Production Optimization through Characterization of Tide-Dominated Deltaic Reservoirs of the Lower Misoa Formation (Lower Eocene), LL-652 Area, Lagunillas Field, Maracaibo Basin, Venezuela

William A. Amborse, Eulise R. Ferrer, Shirley P. Dutton, Antonio Padron, Fred P. Wang, Joseph S. Yeh, Williams Carrasquel, Noel Tyler

Structurally complex and heterogeneous, tide-dominated deltaic reservoirs in the lower Misoa Form LL-652 area of Lagunillas field, Maracaibo Basin, Venezuela, have produced 135 MMbbl of oil but have a low recovery efficiency of 22 percent and will contain considerable volumes of unrecovered mobile oil (900 MMbbl) at the end of primary recovery operations at 80-acre well spacing. The remaining oil resource exists in poorly drained or undrained reservoir compartments defined by a combination of complex structure and depositional heterogeneity with dip-elongate, northeast-trending distributary-channel and tidal-sand-ridge deposits that commonly pinch out laterally between wells at the current spacing of 1,970 ft (600 m).

Maps of hydrocarbon pore volume (So_^phgrh) and remaining oil, based on improved petrophysical characterization and apportioning of production to specific reservoir horizons by kh (permeability feet), indicate that most of the remaining oil exists in the under developed and structurally complicated northern part of the field and also where narrow (less than 2,000 ft; 610 m wide), distributary channel and tidal-sandridge belts of high-So_^phgrh are intersected by a zone of sealing and partly sealing reverse faults. Extended field development on the current well-spacing pattern, strategically targeting infill wells, and waterflooding will result in a 60-percent increase in expected ultimate recovery in the LL-652 area, primarily in the high-porosity C-4-X and C-3-X m mbers, which together represent a major regressive-transgressive depositional sequence in the lower Eocene.

An integrated reservoir-characterization program that includes structural, stratigraphic, petrophysical, petrographic, production-engineering, and volumetric analyses can be used to improve oil recovery operations in other mature petroleum-producing provinces of Venezuela, where many fields are nearing primary depletion. The LL-652 area serves as a model to demonstrate that the most efficient means to cover the remaining oil resource is through a strategy that targets compartments defined by large-scale, depositional-facies geometry and structure.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994