The Relationship Between Sedimentary Rock Compression And Springback Characteristics And Lithology And Pore Structure

The structural deformation of the lithologic association of sedimentary rocks in petroliferous basins is one of the bases for the study of the formation and distribution of unconventional oil and gas reservoirs.Previous research in this aspect is relatively weak.In this paper,the stress-strain curve,lithology,pore structure and rock structure of 152 Upper Paleozoic sedimentary rock samples from the Qaidam Basin of Paleogene Neogene,Bohai Bay Basin Paleogene Neogene and Upper Paleozoic Erdos basin in 38 groups have been analyzed with the achievement of the previous research on stress and strain of rock salt,and on this basis the relationship between the stress-strain characteristics and the lithology of sedimentary rocks(based on the classification of mineral components),the pore structure and the rock structure has been discussed and the structural deformation characteristics of the typical sedimentary rocks association in these three basins has been analyzed.The compression,rebound and fracture characteristics of different lithology samples have been compared under the same axial stress condition;by comparing the data of porosity and permeability with the same lithology and with the result of the comparison of single polarization photographs of samples with similar compression,rebound and fracture characteristics,the main conclusions are as follows.Under the condition of the same axial stress,the strain of salt rock,clastic rock,complex rock and carbonate rock is different,and the result shows that the level from high to low was salt rock,clastic rock,complex rock and carbonate rock.The strain values of particular clastic rock samples are close to that of salt rock due to its high level of porosity.Under the condition of the same axial stress,the strain values of clastic rock with high porosity and high permeability are large,'and the strain values of those with low porosity and permeability is small.The similar trend has also been found in the study of carbonate rocks and the complexes.There is a close relationship between the rock structure of the sedimentary rock and the fracture strength.In general,the fracture strength of the samples with an obvious vertical heterogeneity is small;the fracture strength of the sample with an obscure vertical heterogeneity is large.Under the same stress condition,the magnitude of strain value of a sample reflects its plastic deformation ability.In the group of the salt rock and the complex or the salt rock and the carbonate rock,the salt rock has showed strong plastic deformation ability.In the compressional basin,the salt rock(or salt rock containing gypsum)in the group often takes shape in lenticular structure,and in the extensional basin,the salt rock in the group often forms into "boudin structure".In the group of sandstone and mudstone with high porosity,sandstone with high porosity has showed strong plastic deformation ability;in the compression basin,the plastic transverse compaction of the sandstone in the group occurs,and the mud rocks often break down and develop into parallel surface fractures and oblique surface fractures;In the extensional basin,the plastic transverse extension of the sandstone in the group happens,and the mud rocks often break down and mainly form into nearly vertical fractures.