Lisbon Field: Geology of microseepage

Abstract

Certain satellite sensors can be used for mineral identification and thus detection of alteration indicative of hydrocarbon microseepage. However, care must be taken when placing these results into context because alteration also can be due to other factors. The authors review the rationale for multiscale and multispectral image selection as well as the benefit of iterative processing, to highlight alteration within a given formation. The authors determine using remote sensing results integrated with other geologic information to confirm that alteration exists, compare results with a conceptual microseepage model, reconcile alteration pattern and extent with the geologic setting and trap timing, and appraise the potential that other factors may have caused alteration. The authors used geologic information from the well-studied Lisbon Field including, but not limited to, geochemistry, petrography and diagenetic studies, and paleo-structure reconstruction. We evaluated whether the alteration model made sense by assessing the thermal history and estimating volumetrics and seepage rate based on the geologic setting and extent of alteration. The results confirm that the alteration at the Lisbon Field is compatible with hydrocarbon microseepage as its principal cause, however, it cannot rule out the possibility that some of it may be due to hydrothermal fluid migration.