Geochemical characteristics and source rocks and oil-source correlation of the Lower Cretaceous in Aer Sag, Erlian Basin
Online published: 2014-06-06
Aer Sag is one of the sub-structural units in Erlian Basin, with a lower exploration degree. The Lower Cretaceous is proved the major source rocks and oil-producing intervals in Erlian Basin, which is also widely developed in Aer Sag. The organic geochemical analysis indicates that the Lower Cretaceous source rocks in Aer Sag possess high contents of organic matter, its organic matter type is mainly type Ⅰ and type Ⅱ, and its source rock maturity ranges from low-mature to mature indicating the phase of large amounts of hydrocarbon generating. Among them, the first member of Tenger Formation (K1bt1) has the greatest potential of hydrocarbon generation, and followed by the fourth member of Aershan Formation (K1bt4). The Lower Cretaceous source rocks were mainly deposited in the freshwater to brackish water environment. The redox of K1bt4 preferred to a strongly reducing-weakly oxidizing environment, butK1bt4 tended to a weakly oxidizing environment. The distribution characteristics of regular steranes of the Lower Cretaceous source rocks is “C29>C27>C28”. It is shown that the biogenic sources are dominated by algae input, secondly by terrestrial input. In addition, the correlation of biomarker characteristics of oil sands and source rocks from the Lower Cretaceous suggest that K1bt1 oil originated from K1bt1 itself, but Aershan Formation oil might come from K1bt1 and mixed with the oil from K1bt4 source rocks.
Key words: diagenesis; diagenesis facies; pore types; He 8 member; Ordos Basin
ZHAO Xiaohui , CHEN Juanping , QI Yaling , CAO Qing . Geochemical characteristics and source rocks and oil-source correlation of the Lower Cretaceous in Aer Sag, Erlian Basin[J]. Lithologic Reservoirs, 2014 , 26(3) : 101 -108 . DOI: 10.3969/j.issn.1673-8926.2014.03.017
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