Abstract
ABSTRACT: The Para-Maranhao and Barreirinhas are exploratory frontier basins. After the discoveries in deep/ultra-deep water turbidites at the correlated African equatorial margin and French Guiana (Jubilee and Zaedyus plays), the exploratory interest was retaked for those basins. Using 2D seismic interpretation, it was search to identify hydrocarbon accumulations potential focusing on turbiditic reservoirs. Three plays types linked to three margin distinct segments were identified: shallow waters, faulted shelf border and deep/ultra-deep waters. The shallow waters and faulted shelf border plays are related to two petroleum systems: Caju-Travosas and Travosas-Travosas. The Caju Group (Late Albian-Early Cenomanian) and Travosas Formation (Cenomanian-Turonian) source rocks occur between 2,400 and 3,700 m below sea water bottom for shallow waters play, and between 1,300 and 4,800 m for faulted shelf border play. The deep/ultra-deep waters play is related to three petroleum systems: Codo-Travosas, Caju-Travosas and Travosas-Travosas. The source rocks from Codo Formation (Aptian) occur between 2,860 and 4,550 m, from Caju Group (Late Albian-Early Cenomanian) between 2,200 and 3,800 m and from Travosas Formation (Cenomanian-Turonian) between 1,430 and 2,860 m. In the African equatorial margin, the oil window top is located around 2,700 m below sea water bottom. Thus, it can be concluded that Para-Maranhao and Barreirinhas source rocks would also be able to generate oil/gas in the specified depths.
Highlights
The Brazilian equatorial margin includes Foz do Amazonas, Pará-Maranhão, Barreirinhas, Ceará and Potiguar basins, with shows of oil and gas in exploratory wells along the whole margin, as well as well-known production fields at Potiguar and Ceará basins
The structural framework of Basement and EK sequences is characterized by the presence of large synthetic and antithetical normal faults, commonly configuring horsts and grabens (Fig. 8), which were formed during rift stage of Brazilian equatorial margin and persisted until the end of Albian (Soares et al 2007, Trosdtorf Júnior et al 2007)
Seven wells information available for this research present geochemical data obtained from lateral sample or drill cuttings, and 543 samples were analyzed for the percentage of Total Organic Carbon (TOC), corresponding only 245 samples to Albian to Turonian source rock interval
Summary
The Brazilian equatorial margin includes Foz do Amazonas, Pará-Maranhão, Barreirinhas, Ceará and Potiguar basins, with shows of oil and gas in exploratory wells along the whole margin, as well as well-known production fields at Potiguar and Ceará basins. The depth of Late Albian-Early Cenomanian and Cenomanian-Turonian source rocks at the continental shelf of Pará-Maranhão and Barreirinhas basins occurs approximately between 2,400 and 3,700 m below sea water bottom. At this depth, there is the possibility of oil and gas generation, and more details will be discussed in the next topics. It was inferred that Late Albian-Early Cenomanian and Cenomanian-Turonian source rocks occur approximately between 1,400 and 4,500 m below sea water bottom at Pará-Maranhão basin, and approximately between 1,300 and 4,800 m below sea water bottom at Barreirinhas basin In these depths, there is the possibility of oil and gas generation, the possibility of oil biodegradation to the shallower reservoirs must be considered. The source rocks may be at maturity depth, it can be senile due to the high anomalous temperatures
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