Habitat of Petroleum in the Paleozoic Basins of Brazil: A Look Back, a Comparison, a Look Forward

MEISTER, E. M., J. N. P. CAMPOS, C. BARBOSA FILHO, I. R. BRAZIL, C. A. O. NEVES, A. M. O. GOES, and E. J. MILANI, Petrobras, Rio de Janeiro, Brazil

It took almost a century of intermittent petroleum exploration in Brazil's vast Paleozoic basins before continuous production of about 5000 bbl per day of light oil, together with gas, could be established in one of them. Proved volumes of oil equivalent in place so far discovered in Paleozoic reservoirs amount to only 0.6% of the domestic total, but hopes of substantial new finds are great. In the Rio Urucu field of Solimoes basin (Upper Amazon), hydrocarbons are being produced from Early Carboniferous Monte Alegre formation sandstones roofed by evaporites and carbonates of the Carboniferous Itaituba formation which were intruded by thick Juro-Triassic igneous sills and folded during a Cretaceous reactivation event into the present-day shape of gentle anticlinal trends controlled by everse faulting. The widespread occurrence of igneous intrusions and extrusions in the Solimoes, Amazonas, Parnaba, and Parana basins is a major problem met by explorationists throughout the years but can be faced with presently available technology, seismic and other. Further investigations in these four basins are needed in order to better define details of basin architecture, configuration of basement, location of the oil kitchens, main carrier beds, windows in the dyke walls through which hydrocarbons could find their way to the traps, etc. Examples from the various basins, along with a comparison to some successful exploration cases in the USA, suggest that the habitat of other commercial oil and gas in the Paleozoic basins of Brazil may be localized in the deeper basinal positions- like in the Rio Urucu trend--but also in the shallow flank areas, where igneous rocks tend to be scarcer and exploration baroquely started.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)