Sedimentary characteristics and location within sequence framework of the Qiaotou sandstone of the Taiyuan Formation in Linxing area

eastern margin of Ordos Basin

determine the reservoir type and trap area.The Taiyuan Formation is divided into one complete long-term cycle (LSC1) and four complete medium-term cycles (MSC1

MSC2

MSC3

MSC4) based on identification of sequence boundaries and flooding surfaces by using seismic

logging

outcrop and outcrop data.The Qiaotou sandstone is within the descending half cycle of MSC1 and is dominated by coarse-grained and coarse-to-medium grained quartz sandstones.The cumulative probability curve of the grain size is typical of the two-way flow.Core observation reveals typical tidal current sedimentary structure and pinnate

massive

graded and composite bedding.The sand bodies show lenticular geometry on section and appear as bands parallel with shorelines on map.The Qiaotou sandstone is believed based on a comprehensive analysis to be tidal channel and barrier bar deposits

which are quality reservoirs of marine facies.The sand body parallels shoreline in northwest-southwest direction and all wells that penetrate it test high gas flow.The area of traps are controlled by the sand body boundary and show the characteristics of lithologic traps.This study is of great significance for guiding exploration and development of tight sand gas in Linxing area

eastern margin of Ordos Basin.