The analyses of data from organic petrologic and organic geochemical experiments and testings indicate that the fissured mudstone in the 3rd member of Shahejie Formation encountered in Guo 7well drilled in Jiyang depression was deposited on the lakeshore environment during local transgression.The mudstone is composed of both the harder and the softer components.It has the lithologic composition and textural characteristics of rare reservoirs reported in Santa Maria basin in the U.S.There are two occurrence types of organic matters in the mudstone: one is the dispersed organic matters (mineral-bitumen matrix) that occur in the softer components of mudstone; another are those occur in the harder components of mudstone

including bitumenites in the micropores and microclearances of minerals and free hydrocarbons in the interfissures. Both of them might have come from the same source rock

but the amount of free hydrocarbons that mater occur in the harder components

fissures and pores would apparently be higher than the bitumen in the softer components of mudstone.