Geologic Controls on Reservoir Architecture and Hydrocarbon Distribution in Miocene...Deposits in ...Mioceno Norte Area, Lake M

Facies architecture, structure, and diagenesis control reservoir geometry and distribution of remaining oil in shoreface, fluvial, and deltaic reservoirs of Miocene age in the 18-mi2 (46.7-km2) Mioceno Norte Area in northern Lake Maracaibo. This mature field is undergoing depletion and nearing the final stages of primary recovery. Although the area has produced oil since the 1940's, appreciable volumes of oil (commonly 400 to 1,200 MSTB [thousand stock tank barrels]/20-acre drainage area) remain in multiple, poorly contacted reservoir sandstones at the current 984-ft (300-m) well spacing. Detailed lithofacies maps, documenting the control of sandstone architecture on hydrocarbon distribution, demonstrate that the current well spacing on a grid pattern is too large to recover the remaining oil efficiently. Moreover, the facies architecture influences water-cut patterns and theirregular advancement of inferred oil-water contacts on the west margin of the field. A joint study by the Bureau of Economic Geology and Lagoven, S.A., proposes a variety of infill wells, recompletions, redrilled wells, horizontalwells, and water-injection wells. Approximately 80 MMSTB (million stock tank barrels) of remaining oil will be produced by maintaining the current 984-ft (300-m) well spacing. An additional 46.5 MMSTB, however, can be produced with geologically targeted infill wells, recompletions, and horizontal wells. In addition, new water-injection wells can appreciably increase oil recovery by enhancing sweep efficiency and providing pressure support