Sequence Stratigraphy Of Paleogene And Prediction Of Lithologic Traps In Lixian Slope Of Raoyang Sag

With the theoretical basis of sequence stratigraphy and sedimentology, through the comprehensive analysis of the data related to cores, drilling, logging and seismic, the Paleogene in Lixian Slope of Raoyang Sag can be divided into three second-order sequences and ten third-order sequences. Under the control of macro-sequence stratigraphic framework, with the principle of high-resolution sequence stratigrphy, the Member 2 of Shahejie Formation(SQVI) and the Member 1 of Shahejie Formation(SQVII) can be divided into 6 system tracts with 3 types: lowstand system tract, extension system tract and highstand system tract, and on this basis, these 6 system tracts can be further divided into 11 parasequence sets, based on the logging data by the wavelet analysis. On the base of the sedimentary facies analysis of single well and combining with the characteristics of logging curves and the testing results, braided river delta and lacustrine are identified in the isochronal framework of sequence stratigraphy of SQVI～SQVII. They can be subdivided into 5 types of subfacies and 12 types of microfacies. Through the analysis of single factor maps, such as the sand thickness contour map and percentage of sandstone contour map, the braided river delta plain distributes on the outer belt of the slope,but along the middle belt of the slope the braided river delta-front is widely developed during SQVI and the lowstand system tract of SQVII, as the main part of the sedimentary. While the extension system tract of SQVII is covered by lacustrine , and beach bar and carbonate bank-dam distribute along the shoreline, only in the area of Da Baichi a small delta-front is developed. Meanwhile, during this period, the most important set of hydrogen-rich hydrocarbon source rocks were formed. The highstand system tract of SQVII basically inherited the characteristics of the previous phase, only in the southern region braided delta front develops and the northern region was covered by lakes. The braided river delta-front sandbodies which are low-porosity and medium-permeability and the beach bar and carbonate bank-dam which are medium-porosity and medium-permeability or high-permeability in the middle and inner belts are pinch-out in or wrapped by the dark mudstone. These areas have a good source-reservoir-cap combination, and are the favorable exploration areas of sandstone updip pinch-out reservoirs and lens reservoir.