An Exploratory Study on Density Fractionation and Organic Matter Preservation of Muddy Source Rock

Abstract:

The black muddy rock samples were selected from the deep lake facies of the Shahejie formation,tertiary,in Jiyang depression.By floating with different densities ZnBr2 heavy solution,the samples were divided into many density fractions.A series of detections,including transmission light,florescence,XRD and so on,revealed the difference of organic matter preservation in the different fractions.The analysis results indicate in the fraction ①(ρ <1.6 g·cm-3),the free organic particles are dominant and the minerals do not combine with the organic particles closely.In the fractions of ② and ③(1.6 g·cm-3<ρ <2.2 g·cm-3,ρ >2.2 g·cm-3),the organic amorphous distributes in the fine mineral phase and shows orange and light yellow fluorescence.It indicates the organic matter combines with mineral closely.Further analysis on the organic matter distribution indicates that the fraction ① combines with less than 1% organic matter in the source rock; the fraction ② and ③ combine more than 90% organic matter of the source rock.It reflects the organic matter combining with the mineral is very important way of the organic matter preservation.

Key words:source rock; density fractionation; organic matter preservation