Provenance, diagenesis and reservoir quality of sandstone facies of the Maracangalha Formation, Reconcavo Basin - Northeastern Brazil

Sedimentary composition studies on siliciclastic reservoirs and their relationship with sedimentary provenance have proved to be useful in hydrocarbon exploration, enabling the prognosis of reservoir quality and diagenetic models. However, unconventional terrigenous reservoirs in the Maracangalha Formation, Upper Cretaceous from Reconcavo Basin, have not yet been evaluated regarding sedimentary provenance and its control over reservoir quality. This study aims to define the provenance of the Maracangalha Formation sandstones and its control on the diagenetic processes affecting the reservoir quality. Based on petrography analysis and X-Ray Fluorescence data, it was possible to identify a granite-gneissic terrain under wet climate as the primary source area for quartz -feldspathic sandstones. The granite-gneissic terrains with predominantly felsic minerals, within in the sur-rounding Precambrian Terrains, represent a major source area for the quartz-feldspathic sandstones found in the Maracangalha Formation. These sources are characterized by significant contributions from recycled sedimentary and metasedimentary rocks, leading to the occurrence of litho and quartzose petrofacies. The high chemical -textural sediment maturity and paleoweathering dispersion, under semiumid to semi-arid climates, may be a result of paleoclimatic changes and the variable residence times of the sediments in the dispersion routes or temporary storage. The mineral composition and primary texture of sandstones show a clear influence on diagenetic evolution, particularly in terms of mechanical compaction inhibition, by early cementation, and the generation of secondary porosity due to the dissolution of framework grains and early cements. Therefore, understanding the sedimentary provenance, composition, and diagenesis is crucial for predicting the quality of the reservoir and the compartmentalization of the Maracangalha Formation and its analogues.

Automated summary

This study investigates the sedimentary provenance and its control on reservoir quality in the Maracangalha Formation. Petrography analysis and X-Ray Fluorescence data reveal a granite-gneissic terrain as the primary source area for quartz-feldspathic sandstones. The sources contribute recycled sedimentary and metasedimentary rocks, leading to the occurrence of specific litho and quartzose petrofacies. The mineral composition and primary texture of sandstones significantly influence diagenetic processes and the formation of secondary porosity. Understanding sedimentary provenance, composition, and diagenesis is crucial for predicting reservoir quality.