Organic facies characteristics of Miocene marine source rocks in Yinggehai Basin

To evaluate the Miocene marine source rocks in the Yinggehai Basin, based on the geochemical data of source rocks, the organic facies of the Miocene source rocks were classified, the corresponding relationship between organic facies and sedimentary facies was clarified, and the planar distribution of the source rocks was predicted. Results show that the Miocene marine source rocks could be divided into four types according to the source of organic matter and sedimentary environments: marine terrestrial type, marine mixed source type Ⅰ, marine mixed source type Ⅱ, and marine endogenous type. The corresponding relationship between different organic facies and sedimentation is good, among which fan delta and coastal areas correspond to marine terrigenous types, inner shallow sea corresponds to marine mixed source type Ⅰ, outer shallow sea and half deep sea corresponds to marine mixed source type Ⅱ, and outer shallow sea, semi deep sea and deep sea corresponds to marine endogenous types. Type Ⅱ hydrocarbon source rocks are widely distributed with large thickness and rich organic matters. The organic matter is mainly type Ⅱ₂, and a small amount of type Ⅲ, and have good preservation conditions. They are the main gas source rocks in the Yinggehai Basin. This study provided an important basis for predicting the planar distribution of high-quality marine source rocks in the Yinggehai Basin and accurately evaluating their resource potential.