Fossil traces hold clues to petroleum potential: Porosity analysis of Selorejo limestone formation in NE Java Basin.

This study aimed to investigate the variations of fossil traces in the limestone layers of the Selorejo Formation, as well as the level of rock porosity in the petroleum system. Field mapping, stratigraphic measurements, profiling outcrops, rock sampling, and porosity analysis were conducted to collect data. The results showed that the Selorejo Formation contained various types of fossil traces, such as Planolites, Helminthopsis, Thalassinoides, Conichnus, Chondrites, Macaronichnus, Bergauria, Ophiomorpha, Skolithos, Terebellina Asterosoma, and Palaeophycus. Moreover, rock layers containing trace fossils had lower porosity than those without them. The more trace fossils in the rock layer, the worse the porosity. This finding could be useful in petroleum exploration, as the porosity of rock layers with fossil traces needs to be taken into account when assessing oil and gas reservoir potential. [ABSTRACT FROM AUTHOR]