The geochemical characteristics and metallogenic condition of Permain Lucaogou Formation oil shale in Jimusaer, Junggar Basin, Xinjiang

This paper is the result of oil and gas exploration engineering.

Objective This paper aims to reveal the special metallogenic conditions of high-grade oil shale by comparing the quality and genetic differences between high grade and low grade oil shale of Permian Lucaogou Formation in Jimusaer area, Junggar Basin.

Methods TOC, Rock-eval, oil yield, trace and rare earth elements were tested on outcrop samples collected from two sections in Jimusar area, so as to analysis the difference of organic geochemical characteristics, trace and rare earth element characteristics and metallogenic conditions of high-grade and low-grade oil shale.

Results Research results show that, the organic matter type of high grade oil shale is type I, but the organic matter type of low grade oil shale is type I-II₁. The trace elements contents of the high grade oil shale (such as B, Ba, Cr, Nb, Sr, V, Zr) are significantly different from that of low grade oil shale. The average contents of rare earth elements and the distribution range of rare earth elements in high grade oil shale are smaller than that in low grade oil shale. And elements that are usually enriched in terrestrial detrital minerals of the high grade oil shale is lower than that of low grade oil shale, which shows less terrigenous clastic input of high grade oil shale. The trace elements ratio shows that the oil shale in the study area is formed in warm and humid climate, semi-salty water and reducing environment. Compared to the low grade oil shale, the high grade oil shale was formed with higher salinity water and higher organic matter productivity.

Conclusions Under the background of warm and humid climate, the relatively small supply of terrigenous clastics reduces the dilution and oxidation of organic matters, and high salinity is more conducive to water stratification, thus forming a long-term reduction environment. Combined with higher organic matter productivity, high-grade oil shale is formed.