Sand injectite simulation and formation mechanism analysis
Yi Xuefei1, Zhang Changmin2, Li Shaohua2, Du Jiayuan2,3, Li Kang2,Wang Haoyu2, Li Xiangyang4, Zhou Fengjuan3, Yuan Cai3
1 Hubei Cooperative Innovation Center of Unconventional Oil and Gas,Wuhan 430100,Hubei; 2 Key Laboratory of Oil and Gas Resources and Exploration,Ministry of Education, Yangtze University,Wuhan 430100,Hubei; 3 Shenzhen Branch of CNOOC Ltd.,Guangzhou 510240,Guangdong; 4 Henan Nuclear Industry Geology Bureau,Xinyang 464000,Henan
Abstract：Soft sediment deformation is a common geological phenomenon,which has been focused on these years in the field of geosciences, but less study is on the formation mechanism of soft sediment deformation. A set of laboratory simulation device is designed to simulate the formation and evolution of sand injectites in a simplified three layers model in this paper. On the basis of the former simulation experiments,which only took account of the thickness of the overlying coarse sediment layer and the configuration of inlet pipes,the slope angles of terrain are examined to test the influence of three main variables on the structures formed during fluidization. Also,the formation mechanism is discussed. 7 different shape pipes in different types are observed and the pressures are tested during the experiments. The results show that the thicker the overlying layer is,the slower the pressure drops;the sand injectites finally will erupt out of the surface and turn out to be sand extrusions;unstable terrain is conducive to trigger the deformation of soft sediments. It is showed that overpressure is one of the most important conditions. Compaction disequilibrium and hydrocarbon generation are the two main independent controlling factors of different phases for the development and evolution of overpressure in sedimentary basins.
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