The Tight Sandstone’s Static And Dynamic Rock Physical Characteristics Experimental Study In Mahu Sag

Mahu sag is a secondary negative tectonic unit in the central depression of Junggar Basin,adjacent to the northwest margin fault zone.This thesis mainly by Marjorie lake sag of glutenite sample static and dynamic rock physics experiment,and combined with the feature of sample mineralogy,petrology characteristics,the measurement and analysis of structural characteristics,establish a dynamic and static elastic characteristics and rock characteristics and reservoir characteristics of the experimental relationship,system analysis influence the main factors of dynamic and static elastic characteristics of dense sandstone;The characteristics of elastic anisotropy and its influencing factors of tight sand conglomerate samples were analyzed.The relationship between dynamic and static elastic parameters is summarized.Aiming at the experimental purpose,the rock physics experiment design is carried out,including :(1)core production;(2)petrophysical parameter experiment,including porosity,permeability,whole rock analysis and other tests;(3)Elastic parameter experiment,test the acoustic wave velocity of rock under different confining pressure,pore pressure,axial pressure and saturated fluid,and calculate the elastic modulus.(4)Test of rock mechanics elastic parameters.Under simulated formation conditions,mechanical parameters such as elastic modulus,deformation modulus,triaxial strength and Poisson’s ratio of rock under triaxial compression can be obtained through experimental curves of the whole process of triaxial compression.It lays a foundation for further rock physical analysis.Based on the experimental data,it is found that the mineral composition has more obvious influence on the longitudinal and shear wave velocity relation of the samples,and the velocity ratio(Poisson’s ratio)can be used to distinguish the lithology in the study area.Secondly,there is no identical velocity-porosity variation relationship in the conglomerate sandstone samples as a whole,but the velocity-porosity linear relationship is more obvious in the same sedimentary environment.The effect of particle cementation on mechanical properties of rocks in the study area is greater than the effect of porosity(pore fluid)on mechanical properties of samples.The strength of cement determines the cohesiveness of rock(sandstone)to a great extent,that is,the strength of cement is an important factor affecting the cohesiveness.The decrease of porosity will also increase the cohesion of the rock,and too much debris filling energy will obviously reduce the porosity of the sample and increase the cohesion.The static Poisson’s ratio and detrital content showed a "V" shaped relationship.The longitudinal and shear wave velocities of the samples in different sedimentary environments are obviously different,the linear relationship between the longitudinal and shear wave velocities of the samples in the front facies is more obvious,and the linear relationship between the longitudinal and shear wave velocities of the samples in the plain facies is also better.According to the experimental results(physical parameters,acoustic wave velocity,microstructure parameters,etc.),the dynamic and static elastic parameters of tight sandstone are analyzed.A series of relationships,such as cohesion and compressional wave velocity,Young’s modulus,porosity and detrital content,dynamic and static Young’s modulus ratio and porosity and detrital content,compressive strength and compressional wave velocity,Young’s modulus,porosity and detrital content,were fitted.It provides the basis for petrophysical forward modeling,reservoir logging interpretation and "sweet spot" earthquake prediction.