Study On The Sedimentary Characteristics Of The Medium-deep Buried Strata Of Jizhong Oil-rich Drepression

Based on seismic data, core discretion, and well logging data, this thesis divides the basin margin of the continental fault lacustrine basin into two types: high basin margin and low basin margin, and assesses the type of basin margin in each period of the third and fourth Member of Shahejie Formation(Es3-Es4) in Langgu, Baxian, and Raoyang Depression. During the period of Es3-Es4, Langgu Depression mostly developed high basin margin, Raoyang Depression developed low-basin margin only, and Baxian Depression had the characteristics of both high basin margin and low basin margin, so it is the transitional type of the two types mentioned above. On the basis of the different types of basin margin, combined with the previous study of the sequence stratigraphy and sedimentary systems in each depression, this thesis establishes a uniform sequence stratigraphic framework throughout three depressions, and studies the sedimentary characteristics of the same tectonic belt in different depressions. By comparing the sedimentary characteristics, it can be found that the continental fault lacustrine basin with high basin margin mainly develops nearshore subaqueous fan deposition, which contains more coarse grains in the steep slope belt, and it develops a large scale of mid-deep to deep lake deposition and sublacustrine fan deposition in subsags central belt. The continental fault lacustrine basin with low basin margin mainly develops finer grained fan delta deposition in the steep slope belt, and in the subsags central belt, it mainly develops shore-shallow lacustrine subfacies deposition, the scale of the mid-deep to deep lake deposition is less than that of high basin margin. In the shore-shallow lacustrine belt, the beach and bar deposition is often developed. The slumping turbidite usually develops in the mid-deep to deep lake. Cream salt lacustrine deposition can be developed in low basin margin lacustrine basin when the climate is hot and dry. There is not much difference in the gentle slope belt of these two types, the braided river delta deposition is the main facies in both type of basin. By summarizing the differences of the sedimentary characteristics between the three depressions, it can be found that the tectonic activity is the main factor that caused the differences and the climate also has some affect on it. According to the research above, this thesis summarizes the depositional model about the continental fault lacustrine basin with different types of basin margin. Based on the depositional systems in different periods and combined with the regular distribution and development patterns of the non-structural traps, this thesis predictes the distribution of non-structural traps in these three depressions.