Distribution of Beachbar Sandbodies of the Second Member of Liushagang Formation of Paleogene of South Slope in Weixinan Depression, Beibuwan Basin

Key words: 
• beach bar /
• stratal slice /
• seismic sedimentology /
• distribution characteristic /
• Weixinan Depression /
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Abstract: During the period of the second member of Liushagang Formation, there developed a certain scale  of beachbar sandbodies. Based on the analysis of sedimentary characteristics of beachbar sandbodies, the distribution and evolution characteristics of beachbar sandbodies were studied by using the method and technology of seismic sedimentology. According to the controlling of sedimentary model and the demarcation of drilling data, the analysis of seismic property of stratal slice could image the distribution area of beachbar sandbodies well and could also recognize and distinguish the beach sands and bar sands effectively. The analysis of statal slices indicates that the sandbodies were progradation at the early and middle stage of MC1 cycle and the sedimentary areas of beach sands and bar sands were extended and migratory obviously, while the sandbodies were vertical aggradation at the middle and late stage of MC1 cycle and the thickness and area of bar sands increased obviously. The distribution area of sandbodies was comparatively stable and the beach sands and bar sands were vertical aggradation during the process of beachbar development at the period of MC2 cycle. The bar sands of the two cycles were, parallel to each other as strips, mainly distribution at the southeast and centre parts of studying area. In the interest of increasing the successful rate of wells and prove up the development characteristics of main bodies of beachbar sandbodies, the exploration should be emphasis on the bar sands development area in southeast and centre parts of studying area.