Hydrocarbon generation from Paleogene deep source rocks in Huanghua Depression

Overpressure developed in the Paleogene of Huanghua Depression. Obvious overpressure constraint of deep source rock evolution was found through high temperature and pressure simulation experiment, natural thermal evolution and geological case studies. The R0 profile in Well BS35 is discontinuous with 5 nonparallel segments situated in over-pressured system, low R0 gradients coincide with high TOC, S2 and/or S1 contents, high R0 gradients coincide with low TOC, S1 and S2 contents. This demonstrates that early developed overpressure, high original TOC contents of source rocks and the retention of the pore fluids, are the 3 important factors affecting overpressure constraint of organic-matter maturation, which is quite important for clearly understanding petroleum exploration.