ORGANO-CLAY COMPLEXES IN SOURCE ROCKS——A NATURAL MATERIAL FOR HYDROCARBON GENERATION

Abstract

Traditionally,it is believed that kerogen,a organic matter insoluble in organic solvents separated chemically from source rock,is a material for hydrocarbon generation[1].The procedure to treat samples as such,however,may destroy the original occurrence and relationship between organic matter and clay in source rocks.We extracted an organo-clay complex(2μm) from the crushed source rocks in the depth of 280~3 500 m,in the Jiyang sag,East China.The complex is mainly composed of layered illite-smectite(I-S) and illite with a value of TOC up to 2.62%~9.78%.After treatment with H2 O2,TOC remains as high as 1.23%~4.63%,suggesting that it is the components in which organic matters are enriched.The diffraction peak(d001) of the complex is 1.3~1.4nm at 250℃,and moves to 1.0 nm at 550 ℃ in XRD curves,and the exothermic peaks of the complex is extraordinary stable at 350 ℃ in DTA curves.;The result is consistent in both the XRD and DTA observations.It indicates that organic matter can enter the interlayer space of clay minerals.With PY-GC analysis,the organic matter of C5 and C25 is released from the complex in a temperature range of 250~650 ℃,and reaches a peak at about 450 ℃.Our findings reveal that organic matter can enter interlayer of clay minerals forming a kind of natural and highly stable organo-clay complex,and the composition of the organic matter in the complex is similar to the crude oil.As a kind of natural material,the organo-clay complex plays an important role in hydrocarbon generation in source rocks.