Integrated interpretation of three-dimensional seismic and well-logging data reveals a prominent “pop-up” structure associated with the VLE 400 fault on the regional unconformity between the Eocene and Miocene in the VLE 196 field, Maracaibo basin, Venezuela. The VLE 400 fault family, an eastern splay of the left-lateral Icotea fault in the basin, played an important role in hydrocarbon migration and accumulation in the field. Hydrocarbons accumulated to the east of the fault but not to the west. The “pop-up” structure on the Eocene unconformity has a four -way dip closure, straddling the fault and extending to the west of the fault. Structures of the Misoa Formation, which is the main reservoir developed below the unconformity in the basin, differ from the structure of the unconformity. The structure of the Misoa Formation shows a tilted uplift of the eastern block of the fault dipping toward the east caused by thrust tectonic movements. Thrust movement and following strike-slip movements provided additional accommodation space to the west of the fault and generated expanded thickness of Eocene sediments compared to the area east of the fault. The thickness of the Misoa Formation east and west of the fault shows no significant changes. Expanded sediments overlie the Misoa Formation in the western block in lateral contact with Misoa sediments eastern block act as a lateral seal. Ductile movement of the Guasare Formation shale contributed to the lateral sealing of the fault against the reservoir rocks in the eastern block. Mobilization of the Guasare Formation modified the structure of overlying formations including the anticline of the Eocene unconformity. The growth strata provide useful information of reactivation of e xisting faults, especially subtle movements which are not recognized by conventional seismic interpretation. Growth strata isochrons shows subtle reactivation of the VLE 400 fault family during Miocene time.

In this study, the structure, depositional system, and the seismic stratigraphy of the VLE 196 area, Block V in Lamar Field were interpreted using 3-D seismic data and well logs to characterize structural and depositional settings of the Guasare-Misoa interval. To demonstrate structural settings of the study area 3-D seismic data were interpreted. Three main seismic reflectors, which are the Late Eocene unconformity, Guasare, and La Luna formations, were picked. The most dominant structure in the area is the VLE 400 Fault which was interpreted as a left-lateral strike-slip reverse fault due to its behaviors as a reverse fault in cross sections and as a strike-slip fault in strike sections. The VLE 400 Fault subdivides the VLE 196 area into two main structural blocks, a downthrown block in the western part and the upthrown block in the eastern part of the field where the hydrocarbons were trapped. Several en echelon normal and reverse faults were located along the both sides of the area. The main importance of these faults are that they fractured the La Luna source rock and created migration pathways through the reservoir layers of the Misoa Formation. To interpret depositional system of the Guasare-Misoa interval, tops of the C4 and C5 intervals and associated C4 layers were picked based on well logs and lithofacies maps were prepared. The results of this part of the study show that the sandstones of the Misoa Formation are delta front and fluvial/distributary channel facies of delta system. The net sand thickness map of the C4 interval also exhibits southeast northwest contour patterns reflecting depositional axes in the area. Shaly units of the C4 interval interpreted as potential seals and are of variable thickness and extend. Seismic stratigraphic interpretation of the area shows that the four main seismic facies are dominant which mainly represent the recent sediments, "C" sands of the Misoa Formation, underlying Colon and Mito Juan shales, and basement respectively. Some distributary eroded channel fill structures were also observed within the Misoa Formation, but they were not continuous through the area because of the intensive faulting.