The Characteristics of Sequence Stratigraphy and Lithological Exploration Target in Ying'er Depression of Jiuquan Basin,Gansu Province

Mesozoic continental deposition is developed in Yingr depression of Jiuquan Basin.Depositional and structural research indicates that Lower Cretaceous has the condition of forming lithological oil-gas reservoirs.At present,the research on lithological oil-gas reservoirs is less and the exploration aiming at lithological oil-gas reservoirs is still not developed.In this paper,by the successful exploration experience in faulted depression basins of the eastern China,we attempt to do research on sequence stratigraphy according to drill and seismic data,Lower Cretaceous is divided into four sequences.From bottom to top,there are sequence Ⅰ(lower segment of Chijinpu Formation),sequence Ⅱ(upper segment of Chijinpu Formation),sequence Ⅲ(lower segment of Xiagou Formation)and sequence Ⅳ(upper segment of Xiagou Formation).We lay special stress on dividing the system tracts of major developed sequence(sequence Ⅱ and sequence Ⅲ).Every sequence and system tracts has different response of lithological electric and seismic reflection characteristics.The sedimentary facies and lithological traps are distinguished by 3D seismic attribute inversion and seismic facies analysis etc.Three lithological traps are discovered by the research.Among them,sandbody No.1 has been chosen as a favorable exploration target.