Spores and pollen from crude oils of Weizhou Oilfield in Beibu Gulf of South China Sea

Fifty-eight species of fossil spores and pollen referred to 28 genera and 3 species of fossil algae referred to 2 genera extracted from the crude oil samples were recorded. The samples were collected from the reservoirs within the Lower Liushagang Formation of the Weizhou Oilfield in the Southwest Weizhou Depression of the Beibu Gulf Basin. Based on the comparisons between palynomorphs in crude oils and palynomorphs in potential source rocks, the petroleum source rocks of the protroliferous region were determined. According to the paleoecological characteristics of the original plants producing the spores and pollen, the sedimentary environment of the petroleum source rocks was discussed. The results of the study indicate that the Middle Eocene to Lower Oligocene Liushagang Formation should be the main petroleum source rock series of the Beibu Gulf Basin, and the Middle to Upper Oligocene Weizhou Formation should also contain favorable petroleum source rocks; the petroleum source rocks might have formed in the subtropic lacustrine sedimentary environment under warm and damp climatic conditions.