High-resolution Sequence Stratigraphy And Sedimentary Microfacies Research Into Shawan Formation, Chunfeng Oilfield

On the foundation of high-resolution sequence stratigraphy, petroleum geology, reservoir sedimentology and other theories, this thesis synthetically uses seismic, logging data, cores and other material. According to identification of different kinds of baselevel cycles of Shawan formation and classification of sequence stratigraphic in Chunfeng Oilfield, this study establishes sequence stratigraphic framework, discusses the exhibition features of the sandbody and the distribution of the microfacies, makes certain the sedimentary evolution model, and estimates the reservoir, cap and reservoir-cap association of Shawan formation, in order to guiding petroleum exploration in this area.Three kinds of short-term baselevel cycles are recognize in the study area. Shawan formation in the study area is divided into 7 short-term baselevel cycles, 2 middle-term baselevel cycles and a long-term baseleve cycle. MSC1, a middle-term baselevel cycle composed by braided river deposits, is a set of favorable reservoir with high percentage content of sandbody. MSC2, another middle-term baselevel cycle, the lower of which is mainly mudstones containing thin sandbed and the upper of which is mainly thick sandstones, is deposited by braided fan. On this basis, this study analyses on the provenance of different sandgroup, sedimentary facies indicators, single well facies and logging facies in Shawan formation, combines to the distribution of the sandbody and then makes certain the types of the sedimentary facies. According to the study, the first member of Shawan formation was deposited by braided river, while the second and the third members of Shawan formation were sedimented by braided fan. Braided channel, channel bar and braided plain make up up-deepening short-term baselevel cycles in braided river system. Since the upstream downward, the braided fan can be divided into proximal fan, middle fan and basinal fan. While the first member of Shawan formation was deposited, the provenance was from the northeast. When the second member of Shawan formation was developed, the northeast provenance shrinked and the northwest provenance began to develop. And during the third member of Shawan formation was deposited, the area of the braided fan became larger covering over almost the whole Chunfeng Oilfield.Basing on laboratory analysis material, this study considers that the reservoir of Shawan formation is now in eogenetic diagenetic B period with large pore and medium throat primarily, the physical properties of which is controlled by the distribution of the sedimentary microfacies. Besides, this study appraises and classifies the reservoir, cap and reservoir-cap association particularly. This research shows that there are two sets of reservoir-cap association developed in this area. The first and second sandgroup of the first member of Shawan formation compose to a set of favourable reservoir-cap association in the northwest-center of the study area. The third sandgroup of the first member and the first sandgroup of the second member of Shawan formation constitute another set of auspicious reservoir-cap association in the center of Chunfeng Oilfield.