Abstract
The Parnaiba Basin is a Paleozoic to Mesozoic intraplate volcano-sedimentary basin where the Pimenteiras Formation (Devonian) is the main sequence with potential of hydrocarbon generation, mostly natural gas. The present paper evaluates the potential of hydrocarbon generation of Pimenteiras Formation based on Total Organic Carbon (TOC) and Rock-Eval pyrolysis parameters. In this work, 1077 shale samples of the Pimenteiras Formation distributed in 32 wells were evaluated. The TOC content varies between 0.1 to 4.7 wt.%, partially reflecting the accumulation and preservation rates of the organic matter in marine and coastal depositional environments controlled by regressive-transgressive cycles. The oxic and anoxic conditions vary significantly with deposition in this situation, which were evidenced by HI and OI variations through sample profiles. In the north and center of the basin, the Pimenteiras Formation has a higher potential for hydrocarbon generation relative to the south, probably due to higher anoxic conditions during deposition. The Hydrogen Index indicates the predominance of kerogen types II and III with minor occurrences of types I and IV. The Tmax values indicate general immature conditions and locally postmature, where the lowest temperatures represent the basin´s burial history, whereas the higher ones were influenced by igneous intrusions and thermogenic anomalies related to the Transbrasiliano Lineament. In addition, the excessive heat around the intrusions altered the Rock-Eval pyrolysis parameters as well as the type of organic matter, resulting in a relative increase of the kerogen types III and IV, which explains the great potential for gas generation in this basin.
Highlights
The South American Platform is the stable continental part of the South American plate not affected by the Caribbean and Andean-Phanerozoic-orogenesis (Almeida et al, 2000)
The results show that the majority of samples had Total Organic Carbon (TOC) contents varying from 0.1 to 4.7 wt.% (Table 1), with the higher values classified as being good to very good in source rock potential, according to the definitions of Peters and Cassa (1994)
The data produced in this work provides subsidies to establish the characteristics of the Parnaiba Basin with regards to the quality of shales of the Pimenteiras Formation as hydrocarbon-generating rocks
Summary
The South American Platform is the stable continental part of the South American plate not affected by the Caribbean and Andean-Phanerozoic-orogenesis (Almeida et al, 2000). In this huge Paleozoic platform, sedimentary basins (Parnaiba, Parana, and Solimo~es) developed, of which the Parnaiba Basin is the subject of this study. For Magoon and Dow (1994), an atypical petroleum system is one in which hydrocarbons were generated when an immature source rock within a thin sequence of sedimentary rocks that overlays continental crust is intruded by a dike. In the atypical petroleum system, the source rocks are matured due to their proximity to areas of contact with igneous intrusions, where the geothermal gradient and subsidence are not sufficient for their maturation (Miranda, 2014; Miranda et al, 2018; Cioccari and Mizusaki, 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
