Sedimentary model reconstruction and exploration significance of Permian He 8 Member in Ordos Basin, NW China

XIAO Hongping,LIU Rui’e,ZHANG Fudong,LIN Changsong,ZHANG Mengyuan

Table 1 Comparison of gravel interlayers in He 8 Member cores in northern and south-central Ordos area.

Typical wells Distri- bution Shape and size of gravel Composition and texture of gravel Composition and texture of fillings between gravels Origin analysis Well S7 Northern Ordos area Gravels often appear as triaxial oblate ellipsoids, a small amount in triaxial equiaxed shape. Particle size is generally 1-5 cm. Quartzite is predominant, followed by black chertite with light grey mud gravels. The conglomerate layer has large thickness and poorly sorted gravels Quartz accounts for more than 80%, chert accounts for 5%, and the rest are argillaceous or other debris. Coarse sands in dominance with high shale content, mud-porous cementation Conglomerate deposits by flood events filling channels Well Sh 113 South- central Ordos area Gravels often appear as triaxial oblate ellipsoids, a small amount in triaxial equiaxed shape. Particle size is generally 1-3 cm. Quartzite is predominant, followed by black chertite occurring as interlayer conglomerate with decreased thickness and moderately sorted gravels Quartz accounts for more than 85%, chert accounts for 5%, and the rest are mud or other debris. Coarse sands in dominance with decreased mud shale content, mud-porous cementation Intra-channel conglomerate long- distance transported and transformed