Study On The Sequence Stratigraphy And Sedimentary Facies Characteristics Of Kongdian Formation In Weibei Sag, Changwei Depression

Weibei Sag is an important petroliferous basin within the Tan-Lu fault zone, which has large prospecting potential. Based on the research of predecessors, this paper study on the sequence stratigraphy and sedimentary facies characteristics of Kongdian formation in Weibei Sag, with the using of the theory and technology of high-resolution sequence stratigraphy and the comprehensive research methods of sedimentary system. So it can provide the scientific geological basis for the favorable area optimization during petroleum exploration stage.The leading conclusions are as follows:Based on the comprehensive analysis of seismic data, logging, and cores,5type s of sequence boundaries and the (maximum) flooding surfaces have been recognized. According to correlation of the longitudinal and transverse section,4long-term(LSC1～LSC4),11middle-term(MSC1～MSC11) cycle sequences can be distinguished form Member2of Kongdian Formation and Member1of Kongdian Formation. The structure types and distribution mode of long-term and middle-term cycle sequences have been analyzed and described.According to the principle of high-resolution sequence stratigraphic correlation, we choose the sequence boundary and flooding surface of long-term cycle sequence as the optimum position of isochronous stratigraphic correlation, and the middle-term cycle sequence as the correlation unit, and then, establish the chrono-stratigraphic frameworks of Member2of Kongdian formation and Member1of Kongdian formation.Based on the comprehensive analysis of paleosalinity and paleo-oxygenation, it shows that the sedimentary environment was terrestrial salinized lacustrine during the sedimentary period of Kongdian Formation. The sedimentary system of Kongdian Formation, Weibei Sag is mainly composed of delta and lake system. The sedimentary environment of Member2of Kongdian formation is mainly composed of a reducing or weak reducing deep lacustrine environment. Otherwise, the delta system is mainly composed of steep slop fan delta with a retrogradation to progradational sequence. The sedimentary environment of Member1of Kongdian formation is mainly composed of a weak reducing or weak oxidation shore-lake and shallow-lake environment, and the delta system is mainly composed of steep slop delta with retrogradation sequence.In this paper, with the using of sequence lithofacies and paleogeography mapping, we choose the middle-term cycle sequence as the units of the sand body thickness contour, sandstone/strata contour, sedimentary environment mapping. The sequence lithofacies and paleogeography characteristics and evolution characteristics of Kongdian formation in Weibei Sag have been described in this paper.