Seismic stratigraphy and oil recovery potential of tide‐dominated depositional sequences in the Lower Misoa Formation (Lower Eocene), LL-652 Area, Lagunillas Field, Lake Maracaibo, Venezuela

Abstract

Structurally complex, heterogeneous, estuarine‐delta and tide‐dominated shelf reservoirs in the Lower Misoa Formation (Lower Eocene C Members) in the LL-652 Area of Lagunillas Field in the Maracaibo Basin, Venezuela, had produced 135 million stock‐tank barrels (MMSTB) of oil as of 1993 but have a low recovery efficiency of 22 percent. In an 18-month joint study, the Bureau of Economic Geology (BEG) and Lagoven, S. A., demonstrated that these reservoirs will contain more than 900 MMSTB of unrecovered mobile oil at the end of primary recovery operations at the current 80‐acre well spacing. Two‐dimensional seismic, core, geophysical log, and production data were integrated to improve estimates of hydrocarbon reserves and to identify potential areas for secondary‐recovery projects in Lower Eocene reservoirs in the LL-652 Area. Maps of hydrocarbon pore volume (SoPhih) and remaining oil were derived from improved petrophysical characterization and production apportioning to specific reservoir horizons by permeability feet (kh). These maps indicate that most remaining oil lies in the poorly developed and structurally complicated north part of the field and where narrow [less than 2000 ft (<610 m) wide], high‐SoPhih belts are intersected by sealing and partly sealing reverse faults. The original‐oil‐in‐place resource base of the C Members in the LL-652 area increased by 867 MMSTB (60%) to 2318.2 MMSTB, mainly in the C-3-X and C-4-X Members, by identifying additional reservoir areas and improving quantification of porosity and other petrophysical parameters. Extended development on the current 80-acre [1968-ft (600-m)] well pattern will increase reserves from 127 to 302 MMSTB. However, 116 MMSTB, in addition to the 302 MMSTB, can be produced from 102 geologically based infill wells strategically targeted to tap areas of high remaining oil saturation in narrow sandstone bodies poorly contacted at the current well spacing. Horizontal and inclined wells in steeply dipping strata can capture additional volumes of poorly contacted mobile oil.

Stratigraphic Columns Modeling and Cyclicity Analysis of the Misoa Formation, Maracaibo Lake, Venezuela, using Markov Chains

“…This content diminishes gradually to the southeast, where well 14 achieves the lowest sand value (19.3%). This map also shows a SW-NE sedimentary direction, in agreement with previous geological analyses in the area (Arminio et al, 1994;Cedillo et al, 2004); according to these studies, the thick Eocene fluvial-deltaic sediments prograded eastward and northeastward on the platform (Ambrose and Ferrer, 1997).…”

“…In the central and south parts of the field, a different structural tendency can be observed, characterized by the presence of inverted faults to the west southwest -east northeast direction (Delgado, 1993). The major geological feature in the area is a north-northeast-trending anticlinal dome (Ambrose and Ferrer, 1997). Several structural compartments were created between intersecting faults of diverse age, due to the complex tectonic development of the Maracaibo Lake (Ambrose and Ferrer, 1997).…”

“…The major geological feature in the area is a north-northeast-trending anticlinal dome (Ambrose and Ferrer, 1997). Several structural compartments were created between intersecting faults of diverse age, due to the complex tectonic development of the Maracaibo Lake (Ambrose and Ferrer, 1997). Structurally, the main traps are located along the Icotea high, with Cretaceous and Eocene reservoirs (Yoris and Ostos, 1997).…”

“…According to Talukdar and Marcano (1994) and Delgado (1993), the Lower Misoa strata were deposited in a tide-dominated delta setting with the sediment source located to the west or southwest. Ambrose and Ferrer (1997) describe the Lower Misoa Formation as structurally complex, heterogeneous, with estuarine-delta and tide dominated shelf reservoirs. The C4 sands of the Misoa Formation compresses thick layers of sandstones interbedded with thin shale and siltstone layers (Yoris and Ostos, 1997) (Figure 2).…”

Addressing uncertainty and remaining potential in a mature field. A case study from the Tertiary of Lake Maracaibo, Venezuela

“…2) using biostratigraphy and log response (e.g. Ambrose & Ferrer 1997). In areas of significant Eocene erosion, such as UDW, these intra reservoir picks can be difficult to make.…”