Abstract: The burial depth of Cretaceous Bashkirchik Formation in Bozi-Dabei area of Kuqa Depression, Tarim Basin is more than 6 000 m, and the porosity is mainly distributed between 6%~9%. At the same time, the complex pore structure, significant changes in regional formation water mineralization and geostress result in low contrast in electrical resistivity between gas and water layers. The poor physical properties of the matrix result in poor applicability of non electrical fluid identification methods such as array acoustic rock mechanics parameters and neutron-density envelope. A detailed analysis of regional geological characteristics was conducted to address the identification problem of low contrast in gas and water layer resistivity in the Bozi-Dabei Region, and three electrical identification methods have been developed, including the precise establishment of porosity resistivity intersection diagram method in stress zones, pure water layer resistivity inversion method, and adjacent mudstone resistivity comparison method. At the same time, a non electrical identification method for two-dimensional nuclear magnetic T₁-T₂ intersection map that is not affected by the skeleton was introduced. This fluid identification method was applied to the tracking and interpretation of exploration wells in the Bozi-Dabei Area, interpretation coincidence rate increased by 16.7%, effectively solved the difficulty of fluid identification caused by low contrast of gas and water layer resistivity due to complex geological conditions in the Bozi-Dabei Region. It provides a powerful technical means to avoid oil and gas reservoir leakage in the study area. It has important application and popularization significance in the domestic ultra-deep tight sandstone reservoirs such as the southern margin foreland basin of Junggar, Xinjiang and Hetao Basin of Huabei Oilfield.

Key words: tight sandstone reservoir, poor porosity, low contrast reservoir, 2D NMR, identification method