Paleoenvironmental characterization and evaluation of source rock potential of the Cunga Formation in the Cabo de São Braz Area, Kwanza Basin, Angola
DOI:
https://doi.org/10.70369/8abz8008Keywords:
Cunga Formation, Kwanza Basin, organic geochemistry, source rocks, Rock-Eval pyrolysis, thermal maturityAbstract
The Cunga Formation is a geological formation from Eocene, located in the onshore of Kwanza Basin, consisting predominantly of shale, black mudstone, marl, limestone, siltstone and sandstones. With the aim of characterising the paleoenvironment, and hydrocarbon generation potential of the Cunga Formation in the Cabo de São Braz area, X-ray diffraction (XRD - 24 samples), geochemical analyses were carried out (Total Organic Carbon - TOC 47 samples and Pyrolysis Rock-Eval - 49 samples), and palynomorphs evaluation - 2 samples. It was possible to identify the mineral associations, with the predominance of quartz, albite, microcline, muscovite, and orthoclase. The analysis of palynomorphs revealed the presence of marine palynomorphs, represented by dinoflagellates and foraminifers, and continental palynomorphs, represented by fungi and spores. The TOC values range between 0.14% and 7.52%. The pyrolysis analysis shows the presence of kerogen types II, II/III, and III. The parameter Tmax was used to evaluate the thermal maturity of the samples, with values ranging between 417 °C and 431 °C. These results indicate that the organic matter of the Cunga Formation in the Cabo de São Braz area, although deposited in a favourable coastal to neritic marine environment with good potential to generate oil and gas, has not reached sufficient thermal maturation and therefore has not acted as an effective source rock.
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