Estimativa de porosidades efetivas da formação aquífera Antenor Navarro a partir de ensaios petrofísicos laboratoriais - área da bacia de Coronel João Pessoa - RN.

Abstract

This work shows laboratories measurements of effective porosities in Coronel João Pessoa basin rocks, for estimate basin hydrological reserves. The mentioned basin is located on extreme west Potiguar and is so important for the region, as well indispensable in terms of hydrogeological availability. The basin is inserted on a context of the Brazilian northeast up-country basins, which the origin is linked to the processes of tectonic reactivations in the period of South-American and African continental separation. The geology is lithologically represented for wispy to surly sandstones, siltites and clayey, correlated to Antenor Navarro formation. On this context, were collected eight rock plugs of the region and made laboratories measurements of porosity. Measurements were based on a method of gas expansion (Boyle Law), wherein the porosity calculus is fundamentally realized through the sample filling by a determinate gas. The present study made use of porosimeters that were based on helium gas. The plugs were submitted to measurements at two distinct laboratories. The Laboratory of Engineering of Petroleum Reservoir of UFRN and Laboratory of Advanced Recovery of Petroleum of the UFRJ. At both laboratories the calculated porosity was within the pattern for the lithology of the collected rocks samples, the calculated mean efficient porosity, respectively for both laboratories of UFRN and UFRJ was 27,22% e 27,62%. After, the local hydrogeological reserves were assessed, considering the mean value referred of the efficient porosity of UFRN laboratories, through saturated thickness distincts. The reserves of saturation are of order of 50 x 106 m3 to 300 x 106 m3, for saturated thickness of 64 to 500 meters, respectively.