Geohistory Model and Structural Style for Hydrocarbon Trapping Mechanism in Kendal Sub-basin, North Central Java, Indonesia

The geological complexity of the Kendal Sub-basin is strongly influenced by tectonic processes. These tectonic phases shape the basin's geometry, structural style, and depositional sequences. Structural features contribute to oil seepage manifestations, making this area a promising target for hydrocarbon exploration. This study aims to model the geological history and analyze structural controls on hydrocarbon trapping. The methods used are surface and subsurface geological structure analysis, including recording surface geological structures, fault fracture density analysis, identifying markers from well data, seismic interpretation, subsurface mapping, and making geological history models. Three tectonic phases influence the structural patterns in the Kendal Sub-basin. Beginning in the Early to Middle Miocene, rifting produced a half-graben. The Middle Miocene to Late Miocene north-south compression stage follows this. Finally, the Late Miocene to Late Pliocene fault stage as compression intensity increases, creates a thrust fold zone. The modelling of geological history is closely associated with the hydrocarbon trapping mechanism. Hydrocarbon generation occurs in the organic-rich Lower Cibulakan shale, with vertical migration through fault systems and lateral migration via rock pores until it is trapped in reservoir formations. This migration ceases once the hydrocarbon becomes trapped in the reservoir rock. The study identifies two primary trap types: structural traps (e.g., thrust anticline, sub-thrust, horst block) and stratigraphic traps (e.g., pinch-out sand, built-up carbonate).