Abstract:

Due to the slope background and delta front sandbodies, there are favourable conditions for lithologic trap in Qingshankou Formation of Dabusu area in Songliao Basin. Nine sand groups are divided in intended interval with the method of high-resolution sequence stratigraphy. Delta front, turbidite fan and semi-deep lake are recognized through facies analysis, which are further identified as distributary channel, mouth bar, sheet-like sand, turbidite channel, turbidite sheet-like sand and semi-deep lake mudstones. Constitution and distribution of sedimentary facies are analyzed in each sand group which are based on high-resolution sequence framework. As a result, there are more mouth bar in the sand groups which belong to base-level falling hemi-cycles, whereas more distributary channel in the sand groups which belong to base-level rising hemi-cycles. In studied section, the sandstones in middle and lower part are thicker than those in upper part. The sandbodies are distributed along SW-NE direction and mainly located at the south-western part of the study area. Laterally, the sandbodies turned to be thinner and extinguished to upper direction of NW slope. Based on sedimentary facies distribution and other oil and gas forming conditions, we can draw a conclusion that structure-lithologic trap which are formed due to combination of sandbody distribution and nose structures are the main plays; furthermore, three plays are predicted in Dabusu area, south of Songliao Basin.

Key words: Dabusu area of Songliao Basin, high-resolution sequence, sedimentary facies, lithologic trap