Study On The Characteristics Of The Post-deposition Tectonic Deformation Of The Paleogene-Neogene Lithological Combination In The Zhanhua Sag

In the context of unconventional and conventional oil and gas exploration,the research of the sedimentary rock and its sedimentary tectonic deformation characteristics in the burial process is not yet in-depth.In this paper,based on the above problems,using the Zhanhua Sag as the main research area,combined with the core and sheets observation,the sonic time difference logging data and the stress-strain curve analysis,the characteristics of the lithological combination and the post-deposition tectonic deformation of the Zhanhua Sag are studied,and the following knowledge is obtained:?Main Types of Lithological CombinationAccording to the observation and statistics of the core and sheets of 31 wells,there are mainly two types of lithological combination in the Zhanhua Sag,that is,the combination of the sandstone-fine-grained rock and the combination of fine-grained rock,in which the typical fine-grained rock combination is the siltstone-clay complex combination,the carbonate-clay complex combination,the carbonate-organic matter combination and the gypsum-salt-clay combination.?Characteristics of the Sonic Time Difference of Lithological Combination along with the Variation of the DepthThe sonic time difference logging data of sandstone-fine-grained rock and fine-grained rock of 45 wells in the Zhanhua Sag are selected and the scatter gram of the sonic time difference of sandstone-fine-grained rock and fine-grained rock are plotted along with the variation of the buried depth.The sonic time difference of sandstone-fine-grained rock combination and fine-grained rock combination is rapidly changed in the range of 0-1000 m and slowly changed in the range of 1000-2000 m.?Comparison of Stress-strain Curves of Major Sedimentary RocksAccording to the triaxial rock mechanics test,under the same stress condition,the strain of sandstone in sandstone-fine-grained rock combination is larger than that of fine-grained rock,and the strain of clay complex in carbonate-clay complex combination is larger than that of carbonate rock,the strain of organic matter in carbonate-organic matter combination is larger than that in carbonate rock,and that in gypsum-salt-clay rock combination is larger than that in clay rock.What it more,the larger the strain is,the stronger the elasto-plasticity is,and vice versa.?Characteristics of the Actual Tectonic Deformation of Lithological CombinationsThrough observing the cores and sheets of 31 wells,parallel fractures are developed in the sandstone-fine-grained rock combinations,vertical and oblique fractures are developed in the fine-grained rock combinations.Fractures are developed in the interface and carbonate rocks in the carbonate rock-clay complex combinations.In the carbonate-organic rock combinations,the carbonate rocks develop fractures and the organic matters fill in the fractures.In the gypsum-salt-clay rock combinations,the clay rocks develop fractures and the gypsum-salt rocks fill in the fractures.In addition,the statistical results of fracture development depth show that the fractures of fine-grained rocks are mainly developed below 1800 m depth.?Characteristics of Post-deposition Tectonic Deformation Lithological CombinationsIn the vertical direction,with the increase of buried depth,the tectonic deformation of lithological combinations like sandstone-fine-grained rock combinations and fine-grained rock combinations can be divided into three stages: plastic deformation is mainly in the range of 0-1000 m,elasto-plastic deformation is mainly in the range of 1000m-2000 m,and elasto-plastic-fracture deformation is mainly in the range of more than 2000 m.