Pearson Correlation Coefficient Applied to Petroleum System Characterization: The Case Study of Potiguar and Reconcavo Basins, Brazil

This study applied the Pearson correlation coefficient and principal component analysis as tools for unsupervised qualitative petroleum system evaluation techniques. A total of 252 oil samples (32 features per sample) representative of two Brazilian sedimentary basins (Recôncavo and Potiguar) were used to classify them according to their respective degrees of maturation and origin. The large initial set of variables comprises data on δ13C composition, saturate, aromatic, polar compound fractions, and the techniques reduced biomarkers to the most important variables, maintaining the global pattern of variance. The results were efficient in discriminating different petroleum systems from lacustrine, marine, and mixing sources, as observed in the studied accumulations from the Lower Cretaceous sediments of the Recôncavo and Potiguar basins. The methodology proved to be very useful to vene better characterize the petroleum systems. This methodology can be applied to analyze a large amount of oil samples, using simple software and spending relatively less time

Geochemical Considerations from the Carboniferous Unconventional Petroleum System of SW Iberia

The Baixo Alentejo Flysch Group (BAFG) is an important stratigraphic unit that covers over half of the South Portuguese Zone (SPZ) depositional area, and it is composed by three main tectono-stratigraphic units: the Mértola, Mira, and Brejeira formations. All of these formations contain significant thicknesses of black shales and have several wide areas with 0.81 wt.%, 0.91 wt.%, and 0.72 wt.% average total organic carbon (TOC) (respectively) and thermal maturation values within gas zones (overmature). This paper is considering new data from classical methods of organic geochemistry characterization, such as TOC, Rock–Eval pyrolysis, and organic petrography, to evaluate the unconventional petroleum system from the SPZ. A total of 53 samples were collected. From the stratigraphical point of view, TOC values seem to have a random distribution. The Rock– Eval parameters point out high thermal maturation compatible with gas window (overmature zone). The samples are dominated by gas-prone extremely hydrogen-depleted type III/IV kerogen, which no longer has the potential to generate and expel hydrocarbons. The petrographic analyses positioned the thermal evolution of these samples into the end of catagenesis to metagenesis (wet to dry gas zone), with values predominantly higher than 2 %Ro (dry gas zone). The presence of thermogenic hydrocarbon fluids characterized by previous papers indicate that the BAFG from SPZ represents a senile unconventional petroleum system, working nowadays basically as a gas reservoir

Late Cretaceous cyclostratigraphy and astrochronology based on Natural Gamma Ray of the well-log ES-1 drilled at the Espírito Santo basin (western South Atlantic)

NGR is a geophysical acquisition made by Petrobras at the time of well drilling. Petrobras acquired natural gamma-ray (NGR) data for well ES-1 measured between 1880.6 and 5405.7 m

Late Cretaceous cyclostratigraphy for the subtropical western South Atlantic, Espírito Santo Basin

Well-log data was acquired in a Late Cretaceous section of the Espírito Santo basin (western South Atlantic). Cyclostratigraphic techniques were used to explore the eventual pacing of orbital cycles in the deposition of sequences. The frequency ratio method was used to interpret the orbital cycles and based on this a long-eccentricity signal was interpreted and extracted to create a floating time-scale. Using a seismic horizon associated Cretaceous-Paleogene transition, a strong shift in the natural gamma-ray data was anchored to an age of 66.0 Ma producing an anchored astronomical time-scale placed between late Albian and early Ypresian

Hydrogen Index determination for the well-log ES-1 drilled at the Espírito Santo basin (western South Atlantic) for the Late Cretaceous

HI derives from Rock-Eval pyrolysis using 100 mg of grounded and powdered rock within a Rock-Eval 6 device

Total organic carbon profile of the well-log ES-1 drilled at the Espírito Santo basin (western South Atlantic) for the Late Cretaceous

Rock samples for TOC were dried at 40 ºC and then grounded to a fine powder with subsequent carbonate dissolution with HCl and organic-carbon combustion using a LECO WR 112 Carbon Analyser