HYDROCARBON GENERATION CONDITIONS AND SEDIMENTARY MODEL OF ORGANIC-RICH SHALE FROM CHANG 7 MEMBER OF YANCHANG FROMATION IN SOUTHERN ORDOS BASIN

The study on petrology, mineral composition, organic geochemistry, pore types and sedimentary model of shale from Chang 7 Member of Yanchang Formation in southern Ordos Basin shows that there are three types of mud shale in the area, including massive mudstone of muddy debris flow origin, normal-graded mudstone formed by turbidity current, and laminated mudstone deposited in lentic environment. The former two contain numerous terrigenous clastic minerals, while the latter has high content of carbonate minerals as well as high organic carbon and soluble and pyrolysed hydrocarbon. The kerogens of the mud shale are dominated by type II with minus of type I. The reservoir space of shale is mainly intergranular pore, intragranular pore and microfracture, with rare organic pore. The laminated mudstones are characterized by various pore types and large reservoir space. The massive mudstones formed by muddy debris flow are deposited at the slope toe of lake basin, while the normal-graded mudstone of turbidity current origin and laminated mudstone are widely deposited in the center of lake basin with large thickness.