Integrated computer-aided basin modeling applied to analysis of hydrocarbon generation history in a Northern Italian oil field

Abstract

The application of reaction kinetics to the analysis of hydrocarbon (HC) generation processes requires a detailed temperature history of potential source rocks in order to obtain optimum results. The necessary accuracy can be obtained by employing integrated computer-aided basin modeling techniques to simulate the depositional history, resulting in a continuous record of temperatures throughout the study area. The technique has been applied to the analysis of an on/off-structure HC generation problem in a Northern Italian oil field. The simulation of the geologic processes shows that low sedimentation rates and, more importantly, the high thermal conductivities of the carbonate rocks, resulted in low temperatures throughout most of the geologic history of the study area, which were followed by a sudden, rapid temperature increase in the off-structure area during the last 6.5 ma. The calculated temperature history enables an accurate determination of the HC generation history using a kinetic approach, which shows how HC generation is closely controlled by the sedimentation history and structural development and which also describes its relation to trap formation. It also shows why HCs are generated at very low vitrinite reflectance levels, i.e. peak oil generation at approximately 0.6% R o . Determination of the HC generation rate gives additional, critical information, as even source rocks located in apparently good potential zones at present, i.e. in the on-structure area, can be of minor importance for a trap due to slow generation rates and consequent low expulsion efficiencies.