Abstract: Problems including the difficulty to determine the pinch-out location of cross-well sand bodies in the fine description of reservoir in Sulige gas field,Ordos Basin,usually bring great challenges for the quantitative characterization of sand body scale.To solve these problems,a method which may be applied to determine the pinch-out position of the single period channel in a rapid and quantitative manner,has been established following the fine,comprehensive geological research.That is,the sand-stratum ratio is applied to demarcate the scope of superimposing channels of different stages; under the planar constraints,we analyzed the multistage channel assemblage on the section position,and then described the distribution characteristics of composite channels in the three-dimensional space.A case study of the 2rd submember of the lower 8th member of Shihezi Formation in the infilled pattern test area of Block ST,Sulige gas field,has shown that:① a small-scale layer may be divided into n monolayers of almost equal thickness,and the sand-stratum ratio at the stage i ranges between (i-1)/n and i/n in the superimposing area;② due to the down-cutting of channels and the thinning of sand bodies on river edge,there may be partial deviations in the interpretation of superimposing area,but this does not affect the overall applicability of the methods,and appropriate adjustments to the area are necessary.It is concluded that the method proposed in the study can be applied to immediately identify the spatial distribution range of monolayer channels,and provide technical support for the quantitative characterization of reservoir and prediction of play fairway.

Key words: sand-stratum ratio, spatial analysis, sedimentary stage, area of superimposing sand bodies, monolayer, composite channel, the lower 8th member of Shihezi Formation, Sulige gas field