Carbonate reservoir quality and permoporosity obliteration due to silicification processes in the Barra Velha Formation, Santos Basin, Southeastern Brazil

Silicification is a diagenetic process commonly observed in sedimentary sections of the Aptian carbonate deposits Santos Basin that involves replacement minerals with silica. It mostly associated hydrothermal fluids percolating through faults and fractures. CO2 degassing favors an increase acidity. Consequently, became subsaturated calcite supersaturated Given silica content, two distinct behaviors were identified: reduction enhancement permoporous properties. The aim this work to identify alteration due silicification Barra Velha Formation. To accomplish this, qualitative analysis was conducted correlating acoustic borehole images, nuclear magnetic resonance porosity permeability, elemental capture spectroscopy logs performed, followed by quantitative based on crossplot evaluation. Formation divided into three intervals respect content. common behavior permoporosity increase, but locally, also identified. Finally, we established direct relationship between dissolution precipitation, well-defined trend characterized sonic log (DT) density inverse impedance favored improving lack reservoir qualities intrusive igneous interval.