Research On Sedimentary Facies Of Yingcheng Formation In The North Slope Zone Of Lishu Fault Depression

Lishu depression located in the southeast uplift of Songliao Basin which is a half graben basin controlled by Sangshutai arc fault in the west. Lishu depression were divided into four tectonic zone, named respectively Southeast slope zone, Sangshutai sag zone, Median tectonic zone and North slope zone. The paper focused on the characteristics of sedimentary facies of Yingcheng formation in the North slope zone, researched the characteristics of sequence stratigraphy, the types of sedimentary facies and provenance system, combined with the tectonic setting of North slope zone to analysis the characteristics of sedimentary facies. The paper researches the Yingcheng formation.Based on the regional situation, high-resolution sequence stratigraphy, sedimentology, core, well logs and high-resolution seismic response characteristics, recognized the sequence boundary and the maximum flooding surface, established the high-resolution sequence stratigraphic framework. The Yingcheng formation of North slope zone can be divided into2third order sequences (SQ5、SQ6), four members of Yingcheng formation (the first to the forth), nine sand groups (Y1-SG1—Y4-SG9). Partition the North slope zone and respectively named as Sujiatun secondary subsag、middle erosion slope zone、eastern inherited slope zone. Affected with sedimentation and tectonic movement, the top and bottom strata of Yingcheng formation of the North slope zone are lacuna.Synthesize the characteristics of the core observation, lithologic character, mudstone color, sedimentary structure and fossil, we established the relationship charts of lithology and electric property. There are ten kinds of microfacies and two kinds of sedimentary facies, consist of braided river delta and lake facies. Combined the characteristics of slope structure and palaeogeomorphology, the analysis results of the sandstone decentralized system and seismic attribute, the horizontal distribution characteristics of the sedimentary facies, we assured three provenance systems controlled the North slope zone, they are the northwest, the northeast and the southeast provenance system. All the sand groups of the first member of Yingcheng formation facies mainly include semi-deep lacustrine facy and shallow lake facy, with widespread mudflats deposited overlap. The target zone developed huge area braided river delta facy in the second member of Yingcheng formation, the underwater distributary channel microfacies were developed in the front facy belt. The lake level rose and dropped frequently in the third member of the Yingcheng formation, the front facy delts of the braided river delta and the shallow lake facy delts aggrade alternatively. The sedimentary facy delts moved toward south in the forth member of the Yingcheng formation, the northern delts strata were denuded seriously.With the combanition of the distribution of sedimentary facies and structure characteristics, the thesis statistical analysised the oil and gas bearing features, established the favorable reservoir facies zones of the first member of Yingcheng formation were sheet sand and distal bar in the delta front. The favorable reservoir facies zones of the second member and the third member of Yingcheng formation were the upward tilt zones of delta front in the upside of the slope, the reservoir is mainly with underwater distributary channel sand, the lower side of the slope mainly contained gas, the gas-bearing sand mainly included sheet sand and distal bar of the delta end. The favorable reservoir facy delts of the forth member of Yingcheng formation were the inner margin zones of the delta front, and were mainly developed plain subfacies and underwater distributary channel microfacies.