Abstract:

Based on primary lithology, thermolysis parameter of Lower Paleozoic carbonate source rocks in Ordos Basin,the abundane,types and nature of organic matter in the source rocks are used to determine the maturity and evolution stages of organic matter and estimate hydrocarbon generation ability of the study area. It is considered the kerogen wasⅠ-Ⅱ₁ types with middle-intensity hydrocarbon generation. It is emphasized that hydrocarbon generation of Lower Paleozoic carbonate source rocks can be divided into three phases including four stages, that is, low-maturation phase with R₀=0.65%;maturation phase with R₀=1.50% and high-maturation phase with R₀=2.25%, and the fourth stage of over-maturated pyrolysis gas stage. In this stage, residual kerogen was pyrolyzed and dry gas of high-temprature methan was generated. The source rocks of middle-lower parts of Majiagou Formation and the Cambrian System in the study area are of this stage.

Key words: marine facies, carbonate rock, source rock evaluation, organic matter abundance, Lower Paleozoic, Ordos