Keywords: 
• Mahu sag /
• Baikouquan Formation /
• gravel orientation /
• quantitative characterization /
• orientation degree /
• single well

Abstract: Gravel orientation can be used to judge the environment of coarse grain deposits. On the basis of the analysis and measurement of the gravel image from the core image, using the parameters a and parameters σ to determine the grading orientation and quantitative characterization of gravel orientation in the Baokuquan Formation sandstone in the Mahu sag. The parameter a is the maximum value of the sum of the radii of the gravitational axis of any adjacent three small fans, parameter σ is the degree of deviation of the small fan radius. It is found that the larger the a and σ is, the better the orientation of the gravel is. The method is applied to the Mahu area, and the quantitative division scheme of different levels of gravel orientation has been established:clear orientation (a is greater than 35% and σ is greater than 4), a certain orientation (a is greater than 35% and σ is less than 4), a fuzzy orientation (a is less than 35% and σ is greater than 4), no orientation(a is less than 35% and σ is less than 4). And the directivity of typical seasonal braided channel and temporary braided channel in the study area were studied, the results show that the value of σ in the seasonal braided channel is 4.8~8.13, the value of a is 40%~62%, and the value of σ in the braided channel is less than 4, the parameter a is less than 35%. It can be seen that the method can effectively characterize the orientation of gravel and provide the auxiliary basis for the judgment of sedimentary environment.