Sequence stratigraphy of Lower Ganchaigou Formation in Yuejin Slope, southwestern Qaidam Basin

Sequence stratigraphic studies with high resolution were carried out in the Lower Ganchaigou Formation in the Yuejin Slope of the Qaidam Basin by means of drilling/logging,seismic and natural gamma ray spectrometry logging methods.The Lower Ganchaigou Formation was divided into 2 sections vertically.9 sequence boundaries and 8 fourth-order sequences were identified.Based on core observation,the Yuejin Slope was a braided-river delta,and the study area was mainly of braided-river delta front facies.Combined with the studies of sand body distribution,structure and seismic inversion,2 possible favorable zones of lithologic trap were predicted in sequence Ⅲ of the Lower Ganchaigou Formation.