Provenance Direction and Sedimentary Facies of Chang7-Chang8 Members in Yanchang Formation of Jinghe Oilfield, Southwest Margin of Ordos Basin

Key words: 
• Jinghe oilfield /
• provenance direction /
• Chang 7-Chang 8 sedimentary facies /
• separation of the heavy minerals /
• progradation reflection

Abstract: Based on the studies of the progradation reflections on 3-D seismic data, the matrix mineral assemblages and the heavy mineral assemblages in sandstone cores and the shape of the gamma-ray curves of sandstone, we concluded that the provenance of Chang 7-Chang 8 members in Jinghe oilfield mainly came from the magmatic rocks and metamorphic rocks area which are located in the southwest of the Ordos basin, and the provenance of Zhengning area might come from the south. Cores and logging analysis show that the sandstone of Chang 7₂ member is turbidite sandstone reservoir, which developed nine turbidite water channels or lobate turbidite fans in NE direction. The Chang 8₁ member is a water-transgression sedimentary process from fluvial facies to semi-deep lake facies, which developed three water channels in NE direction and one in NS. The Chang 8₁² member is a shore-shallow lake facial-fluvial facial deposition, which developed underwater distributary channel sandstone; the Chang8₁¹ member developed the water-transgression delta distributary channel sandstone under the background of shallow lake to the semi-deep lake facial deposition.