Siliceous and calcareous sources in marine high-quality hydrocarbon source rocks: skeleton-wall-shell of organism and their debris

Using techniques such as ultra-microscopic organic petrology, the study explores the relationship between bioclasts such as siliceous and calcareous skeleton-wall-shell organism and high-quality hydrocarbon source rocks in terms of their biomolecular composition and stability. Common organisms containing biosilica and siliceous derivatives are mainly radiolarians and other protozoa, sponges, diatoms, chrysophytes, and the siliceous skeleton-wall-shell and debris of some planktonic algae like scales-bearing dinoflagellates. The biogenic calcium preserved in high-quality hydrocarbon source rocks is mainly derived from calcareous skeleton-wall-shell and their debris of animals such as planktonic foraminifera and pteropods and planktonic algae like coccolithophores or acritarchs. These biogenic siliceous and calcareous skeleton-wall-shell debris particles often contain varying amounts of organic matter (pectin or scleroprotein, equivalent to type Ⅲ organic matter), which can generate a certain amount of hydrocarbons at high to over-mature stages and can be preserved in the native pores of biological structures.