Depositional Systems Analysis Of SB28.4~SB26.5in The Eastern Baiyun Sag Of Pearl River Mouth Basin

Baiyun Sag lands in the northern part of the South China Sea, it is located in thepearl river mouth basin in the south of the Zhu II depression, The area is about2×104km2, in this paper the work area is located in the deepwater area of the easternBaiyun Sag. Objective interval is between the lower part of zhuhai formation SB28.4-SB26.5,in this paper, named after SQ4.Sand-shale compaction curve summarizes the law between the speed and depthof sandstone and mudstone: The depth of the baseline of low-speed sandstone (classⅠsandstone) is about2200m, the speed of the clean sandstone above2200m isslightly lower than mudstone,the speed of class Ⅱsandstone is roughly equal to themudstone’s speed, the speed of the most oil and gas sandstone layer and goodphysical property of sandstone is significantly lower than the mudstone’s, the speed ofsandstone and mudstone is very similar between1500-2000m, they are classⅡsandstone, the speed of calcium sandstone between4500-5000m/s, significantlyhigher than that of sandstone and mudstone. Select8wells in the work area andcombined with related data to make the synthetic records, We learn that delta frontsheet sand is a wide range of development in SQ4sequence, sediments are mainlycomposed of sandstone, the second is the sand shale interbed, in addition, there is acertain amount of siltstone deposit, because of the Dong Sha uplift, at the bottom ofthe northeastern research work area of zhuhai formation have developed biohermallimestone deposition. After analysis of single well sedimentary facies and restoringsedimentary basin prototype, we can determine the provenance is the ancient pearlriver at the northwest, the sea level dropped dramatically during this period, deltaforward long distance to the direction of basin, the shelf-break zone present a NE-SW direction in the work area, delta front sheet sand have developed above theshelf-break zone, there is the gravity current deposits under the shelf-break zone, theenvironment of the well T7、T8is gulf shallow slope fan, except the most of theprovenance comes from the ancient pearl river from the northwest direction, there isalso a small part come from the Dong Sha uplift at the northeast direction. Byextracting RMS amplitude attribute our judgment is that carbonate is rich in the northeast uplift area, from northwest to southeast in the order there is gravity currentdeposits、underwater bulge zone、 under-compensation sedimentary environmentunder the shelf-break zone. There are four main water systems, of which three are innorthwest direction, one is in northeast. Delta-deepwater fan depositional system aredeveloped within the sequence, shelf-margin delta is development particularly. Withthe artifical scan interpretation we depict the plane distribution of ZHSB5-s-2thesand group, delta front sandbar is widely developed, have a good reservoir physicalproperties.