The member 2 of Lower Permian Shanxi formation is a main gas-producing reservoir and an important layer for exploration in the mid-eastern Ordos Basin. Outcrop analysis, core observation, comprehensive logging data interpretation and geochemical analysis suggest that the study area was affected by Marine facies at the early-middle stage of member 2 of Shanxi formation. It developed a rivertide controlled delta at the 2 and 3 sub-member of member 2 of Shanxi formation. The delta plain included distributary channel, abandoned channel, peat swamps and interdistributary depression. The delta front included sedimentary micro-facies, such as underwater distributary channel, mouth bar, distal bar, tide sand dam, and interdistributary bay. Seawater pushed out along the southeast Ordos Basin in the age of the 1 sub-member of member 2 of Shanxi formation. The study area developed a river controlled-lake delta on the background of terrestrial lakes. The differences of ancient geographical conditions lead to the different types of sand and reservoir properties. The reservoir sand in the 3 sub-member of member 2 of Shanxi formation was changed by the marine facies completely in the Mizhi-Zizhou and Tawan-Gaoqiao area. It has more advantages in lithologic characteristics, sand thickness and reservoir performance, which are favorable for gas exploration.

sedimentary environments  /  sand-body distribution  /  member 2 of Shanxi formation  /  Ordos Basin