Andrew R. Scott1,
Douglas S. Hamilton1,
Scott D. Rodgers1,
Regulo A. Alvarez2,
(1) The University of Texas, Austin, Austin, TX
(2) PDVSA, Maracaibo, Venezuela
Abstract: Exploitation of mature reservoirs through integrated reservoir characterization, Eocene "B" Sands, Mioceno Norte Area, Lake Maracaibo, Venezuela
Eocene reservoirs in the Mioceno Norte area in the northeast part of Lake Maracaibo have produced more than 508 million barrels (MMSTB) of oil since 1930. However, multiple, poorly contacted reservoir compartments in heterogeneous fluvial-deltaic sandstones, a regional unconformity, and complex patterns of closely spaced faults have resulted in recovery efficiencies of less than 15 percent. Tremendous reserve-growth opportunities exist in these mature reservoirs because of structural and stratigraphic heterogeneity.
Advanced reservoir characterization and integration of geological, engineering, and geophysical analyses was performed by (1) determining geologic reservoir architecture within a high-resolution sequence stratigraphic framework, (2) establishing fluid-flow trends in the reservoir, (3) integrating reservoir architecture and fluid-flow trends to identify fundamental reservoir heterogeneities and developing three-dimensional flow-unit models of the reservoir, and (4) calculating volumetrics to estimate original oil in place, residual oil saturation, and remaining mobile oil. Reserve-growth opportunities become apparent when shortfalls in production as compared with remaining mobile-oil resource are identified. The integrated reservoir model provides the basis for geologically targeting potential infill and step-out drilling locations, recompletions, and field-management strategies. Combining reservoir architecture with virtual-reality visualization, 3-D seismic, and production data resulted in a four-dimensional, time-lapse visualization of fluid migration (gas injection and water drive) within the Eocene B6 reservoir over 46 years. Fault transmissivity and bypassed compartments are readily identifiable with virtual-reality visualization. Integrated reservoir characterization resulted in identification of approximately 1.9 BSTB of remaining mobile oil and the delineation of numerous infill and recompletion wells. If only 10 percent of the remaining mobil oil is recovered, then an additional 190 MMSTB may be produced from this mature field.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana