Abstract:

The organic matter laminae composed of algae and its decomposition products is very abundant in argillaceous dolomite and dolomitic mudstone of the Lower Cretaceous in the Jiuxi Depression. The development of algae laminae greatly enhances the hydrocarbon generating ability of source rocks in the research area and is one of important reasons why the source rocks are heterogeneous. In this paper, development and reservation environment and formation mechanism of algae laminae in the Cretaceous source rocks are discussed, and the formation mechanism of algae laminae is probed. The research results show that in the early Cretaceous, the capaciousness of lake water, moderate temperature and salinity are favorite for the algae blooming. However, the strong reductive environment made by layering of lake water is greatly of advantage to reservation of organic matters. Seasonal change of lake water and its layering are the important reasons of the formation of algae laminae.

Key words: source rocks, algae laminae, development condition, formation mechanism, Jiuxi depression