Structural reconstruction and oil prediction in the Roncador Field, Campos Basin, Brazil

Abstract

Geological studies and interpreted seismic section revealed an important structural inversion that occurred in the adjacent area of SE Roncador Field (Campos Basin) and affected a local oil accumulation. As the result of this inversion, the area close to a former depocentre came to occupy a higher structural position. In the same area, data obtained from two exploration wells revealed that the reservoirs near the structural high do not contain oil or indications of hydrocarbons. However, in another well located 1 600 m down dip from the first, the same reservoirs are characterized by a section over 100 m thick with oil shows, and the upper interval containing 16 m of residual heavy oil. Interpretations are that the oil shows found in the thick section of reservoir rocks indicate a paleo accumulation, today situated in a lower structural position due to tilting. The final result was that the general movement of the structure affected the oil accumulation, in such a way that the hydrocarbons escaped through an extensive fault zone delimiting the ancient structure. Also discussed is the sequence and timing of the events intervening between the formation of the trap and the precocious migration of hydrocarbons, as well oil retention aspects in the area to the SE of the Roncador Field.