Study On Plastic Deformation,Elastic-plastic Deformation And Fracture Characteristics Of Sedimentary Rocks In Zhanhua Depression

Studies on the lithology of sedimentary rocks also lack the classification of rock types based on the content of mineral components. At the same time, previous studies on the plastic, elastic-plastic and fracture characteristics of sedimentary rocks with different compositions are also weak. All of these situations restrict the further understanding of the process and mechanism of oil and gas accumulation. This article in view of the weak link, select Zhanhua sag as the study area.Through a series of studies, including rock mechanics experimental study, sedimentary rocks with the buried depth of the mechanical properties evolution research and feature observation of cracks in core and thin, discussed the characteristics mechanism and development area of fracture development in different types of composite formation,under extensional environment, and gives the model.Observation and Research on the development of fracture in the mutual layer:the formation of the mutual contact area of the various combinations are all developed parallel to the crack; Mudstone in sandstone and mudstone interaction, is easier to develop high angle oblique; in organic matter and calcareous interbed, vertical cracks mainly exist in the calcareous layer rather than in organic matter. Some vertical cracts are filled with black component of organic matter.; n dolomite and mudstone interbed, vertical cracks mainly exist in the dolomite layer rather than in mudston; in porous rock(rock with large amount of cast body filled pores in the cast sheet) and compact rock(rock with no or very rare cast in the pore of the cast body) interbed, vertical cracks mainly exist in the compact rock layer rather than in porous rock.The experimental results of compression, rebound and fracture of sedimentary rocks in Zhanhua depression are obtained:(1) Under the same vertical load, the vertical compression and resilience of the clastic rock, the mixed rock and carbonate rock are weakened, and the extension of the horizontal direction is also decreased. (2) Clastic rock with dominant pore structure and loose structure, its vertical compression and radial extension are better than that of clastic rock with hidden pore structure and compact structure. In the process of loading and unloading, the clastic rock carbonate rock is not easy to break, the most easy to produce cracks.Based on the statistics of the fracture development depth and the evolution of the rock mechanical properties during the settlement of the sedimentary strata in Zhanhua depression, it is found that the buried depth of formation plastic compaction stage is 0-2100m, and the buried depth of plastic compression and fracture stage is below 2100m.Synthesis of the above research:There are differences in mechanical properties of rocks with different components and structures,.Therefore, under the same stress condition, they show relative rigidity and plastic characteristics in the mutual layer formation. In Paleogene-Neogene strata of Zhanhua sag, "?"-shaped composite crack formation, and "stone sausage" tectonic belt are developed under 2100m.