George Jamieson

Time-Depth Converted Interpretation of Regional Seismic Maps, Offshore Southeast Brazil

Regional seismic interpretation mapping of the pre-stack time migrated data produced seven key sequence boundary maps: Sea-floor, Intra-Oligocene, Top Cretaceous, Top Albian, Top Salt, Base Salt and Top Basement. Iso-time maps were subsequently constructed for the major tectono-stratigraphic mega sequences: syn-rift-lacustrine, transitional-transgressive and drift-open marine. Significant structural elements in each of these time maps are herein described and discussed. The depth conversion of each regional map adds considerably to the structural interpretation. Most of the regional structural features are in deep-water; hence the bathymetry correction itself affects the visualization of structures. It is well known that residual misties needs adjust the mapping of depth along non-dip lines. Hence, our depth conversion of deep-water maps was adjusted for these. Several of the dip-lines utilized were pre-stack depth migrated, but mostly with seismically derived velocities over the large deep/ultra-deep-water realm.

Regional Evaluation And Hydrocarbon Potential of the Deep Section of the Gulf of Mexico Offshore Louisiana Continental Shelf From Modern 3D Seismic Data

A regional interpretation of the central and outer Louisiana continental shelf has been undertaken, utilizing a reprocessed 3D pre-stack time migrated seismic survey. This survey forms contiguous coverage over 1050 OCS blocks across West and East Cameron, Vermilion, South Marsh Island, Eugene Island, Ship Shoal and South Timbalier. This dataset shows improved resolution of structural and stratigraphic features at depth, compared to previous datasets in the region. This is crucial for improving both regional understanding and raising the confidence of deep Miocene section prospect evaluations. The interpretation of this new seismic dataset has revealed a number of interesting structural and stratigraphic features in the relatively unexplored Middle to Lower Miocene section.

Deepwater exploration potential of the Santos Basin from recently acquired seismic data

Summary The deepwater regions of Brazil’s continental margin basins are attracting increased attention from exploration companies. The most recent offshore Bid Round, number 3, scheduled for June 2001, is focused on the deepwater regions of offshore Brazil. Of the 43 offered blocks, 31 lie in the deepwater region, with 12 of these deepwater blocks located in the Santos Basin. Many large oil fields have already been discovered in the deepwater Campos Basin, such as Marlim and more recently Roncador. By comparison, the deepwater region of the Santos Basin has been less explored and is less understood, the single discovery to date occurring in late 1999. This paper outlines the encouraging hydrocarbon potential of the deepwater Santos Basin by utilizing a recently acquired, processed and interpreted 2D dataset which has revealed numerous, largely untested, play types. These plays include both structural and stratigraphic components. Salt-related large 4-way closures, including faulted and unfaulted turtle structures and drapes over salt have been identified along with sub-unconformity traps. All these identified play types have examples with associated amplitude anomalies, which are widespread throughout the basin, at varying stratigraphic and structural levels.

Seismic comparison of deepwater fields of the Gulf of Mexico and offshore Brazil

1. Summary This study compares five deepwater fields, Mars and Diana in the Gulf of Mexico and Roncador, Marlim and Albacora Leste offshore Brazil. These reservoirs occur in basin floor fan, prograding wedge and slope fan systems tracts. Recently acquired 2D seismic data show them to consist of high amplitude high continuity and hummocky lower continuity reflectors. The Gulf of Mexico field examples occur in minibasins surrounded by massive allochthonous salt canopies. The Brazil examples are controlled by massive but autochthonous salt. Hydrocarbon migration into the Brazil fields is from a syn-rift source via large faults, which breach the salt where it is welded. Migration into the minibasins of the Gulf of Mexico is more complex due to the allochthonous salt but will probably be via salt-welded minibasin floors.

Interval velocity slices: A potential lithology tool in deepwater Gulf of Mexico

An average velocity cube was generated from DMO corrected stacking velocities along 30000 line miles of 2D seismic (Figure 1). Checkshot surveys from 107 wells were used to calibrate the cube. Interval velocity time slices over fixed time intervals were extracted from the cube, using the water bottom time as a datum. Interval Velocity contour maps of each time slice were calibrated to sand content from well logs within the velocity cube. A top of overpressure grid, resulting from the velocity cube generation, was used in the assessment of basin geometry and major structural features.

Structural evolution of western offshore Nile Delta

Structurally, one of the most striking features of the offshore Nile Delta is a major NE-SW striking pervasive normal fault which occurs in the western pat-l of the cone. There is a corresponding uplifted zone of deeper reflectors on seismic data associated with the fault. This uplifted block appears to have initiated faulting no later than Middle Miocene times with a related phase of shale diapirism. Further reactivation of the fault has occurred in Messinian times and throughout the Plio-Pleistocene.