Campos Basin

Integrated Study of The Petroleum Systems

The region known as Cabo Frio is located offshore Rio de Janeiro state, bounded by the southern portion of the Campos basin, an uplifted basement area (the Cabo Frio High), and the northern portion of the Santos basin (map above). Geochemical Solutions International (GSI) has conducted an assessment of the regional petroleum potential in a study entitled Integrated Study of the Petroleum Systems in the Cabo Frio Region. It employs a varied technical approach consisting of:

Analysis of 12 Radarsat-1 images to detect sea surface oil slicks

Analysis of 168 sediment cores to detect oil seepage at the seafloor

2D basin model to evaluate hydrocarbon charge and timing of migration

Geochemical analysis of 14 sub-surface oils to characterize oil quality

The results have been interpreted to define the active petroleum systems, subsurface migration pathways and hydrocarbon compositions expected in this region. This information is relevant to the assessment of several deep-water blocks in the Campos and Santos basin that are being offered as part of the ANP Round-3 bid round.

A technical description of the individual data sources is included below:

Detection of sea bed oil seeps
Seeping oil and gas in seabed sediments can be used evaluate hydrocarbon charge at both regional and sub-regional (prospect) scales. A total of 168 sediment cores have been collected at potential oil and gas seepage sites throughout the southern Campos basin in ANP Round-3 blocks BM-C11, BM-C14, and BM-C15, and ANP Round-2 blocks BM-C7 and BM-C8. Geochemical analysis indicates the presence of hydrocarbons at various locations that originate from the deep subsurface. These occurrences are associated almost exclusively with deformation and uplift of the near-surface sediments, which presumably represents conduits along which hydrocarbons migrate to the surface. A correlation with oils from nearby wells defines the hydrocarbon source facies and suggests subsurface migration pathways.

Detection of natural sea surface oil slicks
Detection of natural sea surface oil slicks in satellite images can be used as independent evidence for present-day hydrocarbon generation and migration. Twelve RADARSAT-1 W-1 images acquired between July and November 1998 over the Cabo Frio region have been analyzed for the presence of natural sea surface slicks. Slick features were identified using a classification algorithm and ranked according to tectonic setting, temporal persistence and predominant environmental conditions. The results are presented over digitally enhanced bathymetric maps as well as a structure-contour map of the top of the evaporites in order to relate the surface slick to major subsurface structural features. 2D seismic data are also integrated in order to identify possible locations of hydrocarbon emanations resulting in the slick feature.

2D Basin model
Numerical modeling has become an integral part of exploration strategy, which simulates basin evolution and petroleum generation, expulsion and migration in a physically consistent manner. GSI has teamed with BEICIP-FRANLAB to perform a 2D compositional basin model of a regional geologic cross-section in the southern Campos Basin using the Temispak 2D software. The model addresses the following aspects of regional petroleum systems: 1) location and evolution of petroleum kitchen areas; 2) timing of petroleum generation, expulsion and migration; 3) migration pathways, accumulation and losses; 4) oil and gas compositions.

Geochemical analysis of oil samples
Fourteen samples from ten wells have been analyzed using state-of-the-art oil fingerprinting techniques to evaluate the major factors governing oil quality and volumes including: (1) source facies, (2) thermal maturity, (3) distance of migration from source to trap, (4) extent and timing of biodegradation, and (5) degree of oil mixing.

The results of these individual studies have been integrated in a petroleum systems context to define the principal source rocks and kitchen areas, migration pathways and hydrocarbon compositions expected for the Cabo Frio region.