Sedimentary characteristics and petroleum geology of sublacustrine fan of the upper section of the first member of the Tenger Formation in the Aer Sag of the Erlian Basin

The upper section of the first member of the Lower Cretaceous Tenger Formation in well Aer1 and neighboring area in the Aer Sag of the Erlian Basin is an oil-bearing formation sourced from a sublacustrine fan according to core, grain size, logging and seismic data. This fan is marked by abundant load structures, normally graded bedding, massive bedding, and incomplete Bouma sequences. Well logs show finger shapes on a background of low resistance and high GR values. Seismic profiles are characterized by lenticular shapes. A middle fan with obvious channels and a lower fan without significant channels have been recognized on seismic profiles. Source rocks surround massive sandstones or normally graded sandstones in a sublacustrine fan, with relatively high porosity (average 16.6%) and permeability (average 282×10^-3 μm²) can be regarded as favorable petroleum reservoir.