Roberto Fainstein

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.

Seismic Signature Comparisons of Deepwater Producing Provinces

This paper performs comparative seismic investigations of reservoir responses in the main producing deepwater provinces of the world, i.e., Gulf of Mexico, offshore East Brazil and offshore West Africa. These fields occur in basins that have been shaped by salt tectonics overlying sub-salt sequences predominantly located in the slope and rise. Exploration of these basins accelerated in the last decade, extending the drilling activity now to the continental-oceanic crust (cob) boundaries.

Time/Depth Imaging Offshore India

Prestack depth migration (PSDM) projects of regional lines and 3D surveys have a major impact on exploration and development projects offshore India because the technique can reduce risks. PSDM can handle complex structures and rapid vertical and lateral changes in the velocity field, so the resulting images can enhance interpretations compared to those based on the time processing results alone.

Offshore Brazil 2005 - Regional Update and Future Exploration

Summary Offshore geophysical data acquisition and offshore drilling have had an impact on every aspect of the Brazilian offshore petroleum industry since 1999. Seismic programs, massive non-exclusive, spec 2D and 3D data acquisition programs were conducted offshore the Brazilian coast at record pace in the last six years and were followed by diverse deep-water drilling programs. The new geophysical data libraries offshore Brazil brought modern technological era to seismic interpretation, prospect evaluation, reservoir characterization and reservoir geo-steering during deepwater development drilling. The main producing basins offshore Brazil are situated in the east coast. Modern seismic interpretation has mapped, through high resolution imaging, the stratigraphy of hydrocarbon producing turbidite reservoirs, has posted correct geometries of salt structures and, beneath the salt, has uncovered the structures of the underlying syn-rift sequences that encompasses most oil bearing source rocks. Offshore, in the eastern and northern coasts of Brazil the seismic data acquisition targets the mapping of new reservoirs in deep water and their relationship with rift sequences source rocks. Seismic resolution of whole lithologies offshore Brazil has improved substantially with the new technologies employed in data acquisition, data processing and data interpretation. Pre-stack time migrations with higher order NMO are now routinely performed whereas selected regional lines have been pre-stack depth migration processed. Regional 2D and 3D surveys acquired with long cables and large foot-print have provided new data libraries along the whole continental margin off Brazil, this modern portfolio of regional surveys 2D and 3D are larger in size to all historical data. The results of regionally interpreted seismic lines and regional mapping of the outer shelf, slope and deepwater provinces of Santos, Campos and Espirito Santo basins are presented herein. The deepwater turbidite plays along the continental slope are interpreted from the modern data that allows for precise resolution image of the syn-rift source rocks, salt architecture, migration paths through faulting and salt windows, reservoir characterization and regional seal mapping. Future offshore exploration hence will continue aiming at better seismic resolution of the deepwater prospects and into the ultra deepwater plays of the salt wall mini-basins, the last frontier region of the continental crust petroleum province.

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.