Caracterização petrofísica e avaliação do potencial de acumulação dos hidrocarbonetos na parte sul do bloco de Inhaminga/Baixo Zambeze

Abstract

This work focused on the petrophysical characterization of the reservoirs found along the Savane-1 well, located north of the Mozambique Coastal Plain (MCP), drilled by the Norwegian company DNO in 2004 and considered technically dry. The primary and secondary targets were Late Cretaceous geological structures, specifically in the Lower Grudja Formation, deposited in the Campanian-Maaestrichtian interval (G9 to G12). The main objective of this scientific project is to identify potential hydrocarbon reservoirs using conventional electrical diagrams of the Savane-1 well. The study involved detailed lithology analysis, analysis of the reservoir fluids, and determination of petrophysical parameters such as clay volume, porosity, permeability, fluid saturation, and net sand thickness. Available data sets were used, including Gamma Ray (GR), Spontaneous Potential (SP), Caliper (CAL), Resistivity (HLLS, HLLD), Neutron (NPHI), Density (RHOB), and Sonic (DT). The Techlog platform version 2015.3 was used for data analysis, and Petrel 2017 was used for earthquake-stratigraphic mapping. This study identified three potential reservoirs of Maastrichtian (Zone 1) and Santonian-Turonian (Zones 2 and 3) age, composed primarily of sandstone, with clay intercalated in some layers, which were analyzed in detail. In general, in the three identified reservoirs, effective porosity in zone 1 averages 34.2% and 31% in zones 2 and 3, respectively, suggesting a differentiated capacity for hydrocarbon accumulation. Resistivity in all three zones presents relatively low values, ranging from 0 to 3.5 ohms, indicating a low potential for hydrocarbon accumulation. However, Zone 3 showed evidence of hydrocarbon manifestations in the Upper Dome Clay Formation, distinguished by its economically attractive properties. The fluid types defined in the reservoirs, based on the neutron-density and resistivity profile signatures, indicate the presence of two fluids in the reservoir: water and gas. The high water saturation, reaching approximately 80%, indicates a high proportion of void spaces occupied by water, resulting in low hydrocarbon saturation. The results show that the hydrocarbon potential in the Savane-1 well is low due to the small reservoir thicknesses in Zones 2 and 3 (2,713 and 5,471 meters respectively), and the low hydrocarbon saturation.(TRADUÇÃO NOSSA)