This study investigates the effect of thermal maturation and organic matter content on the fracturing of oil shale in the Pabdeh Formation, a source rock in the Zagros Fold-Thrust Belt. The research combines Rock-Eval, Iatrosan, and electron microscopy to analyze samples before and after heating. The study reveals that microfractures initially form at the tips or edges of kerogen and are filled with hydrocarbons. As catagenesis progresses, the pressure caused by the volume increase of kerogen decreases due to hydrocarbon release. The transformation of solid kerogen into low-density bitumen/oil increases pressure, leading to the development of damage zones. The small porothroats in the Pabdeh Formation hinder effective expulsion, causing increased pore fluid pressure inside initial microfractures. Accumulated stress due to hydrocarbon production reaches the rock's fracture strength, further contributing to damage zone development. Microfractures preferentially grow along low-strength pathways, such as lithology changes and laminae boundaries. When the pore pressure created by each kerogen overlaps, individual microfractures interconnect, forming a network of microfractures within the source rock. This research provides valuable insights into the complex interplay between temperature, hydrocarbon generation, and microfracture development in the Pabdeh Formation, aiding in the understanding and optimization of hydrocarbon extraction in similar geological settings.This study investigates the effect of thermal maturation and organic matter content on the fracturing of oil shale in the Pabdeh Formation, a source rock in the Zagros Fold-Thrust Belt. The research combines Rock-Eval, Iatrosan, and electron microscopy to analyze samples before and after heating. The study reveals that microfractures initially form at the tips or edges of kerogen and are filled with hydrocarbons. As catagenesis progresses, the pressure caused by the volume increase of kerogen decreases due to hydrocarbon release. The transformation of solid kerogen into low-density bitumen/oil increases pressure, leading to the development of damage zones. The small porothroats in the Pabdeh Formation hinder effective expulsion, causing increased pore fluid pressure inside initial microfractures. Accumulated stress due to hydrocarbon production reaches the rock's fracture strength, further contributing to damage zone development. Microfractures preferentially grow along low-strength pathways, such as lithology changes and laminae boundaries. When the pore pressure created by each kerogen overlaps, individual microfractures interconnect, forming a network of microfractures within the source rock. This research provides valuable insights into the complex interplay between temperature, hydrocarbon generation, and microfracture development in the Pabdeh Formation, aiding in the understanding and optimization of hydrocarbon extraction in similar geological settings.