Lithology, Sedimentary Environment and Organic Contents of Carbonate Source Rocks.

The importance of the carbonate rocks as reservoirs is underscored by the fact that they are host to about 46 percent of the oil in the “giant oil fields”. So, lately the studies have been published on the carbonate source rocks and organic geochemistry of the carbonate rocks.However, the objects of those studies were not limited on the source rocks of “reservoir oil”. Consequently, some of those studies conducted the incorrect conclusions.The object of this study is limited on the source rocks of “reservoir oil”.The lithology of the carbonate source rocks of “reservoir oil” is the impure and/or argillaceous carbonate rocks.These carbonate source rocks are deposited on the stable shelf, intershelf, platform or ramp with minor episodes of terrigenous influx. Water depth of the sedimentary environments are intertidal to subtidal or shallow to moderately deep marine. These environments are essentially anoxic or disaerobic.Total organic carbon contents of the carbonate source rocks are 0.5wt.% and over, and these values are equivalent to the contents of the shale source rocks. And EOM and HC contents are equivalent to EOM and HC contents of the shale source rocks too.The CPI values of extracted n-alkane are 1 or less than 1.