Research On The Inversion Method Of Rock Permittivity Based On The Microwave Radiometer

The dielectric properly of rock is an important characteristic of its electromagnetic radiation property,and the dielectric constant,as the core physical parameter of the dielectric property,represents the propagation,absorption,scattering and other characteristics of rock to electromagnetic wave,which is the most basic physical parameter to describe the electromagnetic radiation of rock.In view of the requirements of rock specimen processing accuracy in the current rock dielectric constant test and research,the preparation is difficult,and most of the methods can only measure the local and surface area of the rock dielectric constant,which can not represent the overall dielectric properties of the rock.Based on the theory of microwave radiation transmission in layered media,this paper establishes the functional relationship between the brightness temperature of microwave radiometer and the dielectric constant of rock,further proposes a new method for the inversion of the equivalent dielectric constant of rock based on the brightness temperature of microwave radiometer,carries out the experiment of the inversion of the dielectric constant of rock based on microwave radiometer,and synchronously uses the traditional method of open coaxial cavity and waveguide method for the inversion The experimental results show that the water content of sandstone influences the depth of microwave penetration:(1)Based on the experiment of microwave radiometer brightness temperature inversion,the equivalent permittivity of the rock sample to be measured is effectively inverted.The results show that the real relative error of the two methods is 2.85%,and the virtual relative error is 18.10%.By analyzing the limitation of the two methods,the feasibility and the correctness of the inversion model based on the brightess temperature of microwave radiometer are preliminarily proved.(2)When the water content of sandstone is in the range of 0～2.60%and the frequency of microwave radiometer is at 6.6GHz,with the increase of water content,the real part of dielectric constant of sandstone decreases first and then increases,the imaginary part of dielectric constant increases gradually,and the penetration depth of sandstone decreases exponentially,the maximum penetration depth is 54.02cm,and the minimum penetration depth is 3.80cm.This study provides a new method for the measurement of the permittivity,which is more convenient and effective to perform the equivalent permittivity under the complete structure of rock.It avoids the disadvantages of contact local measurement,surface measurement and complex specimen preparation in the previous measurement of the permittivity of rock,enriches the measurement methods in the field of the measurement of the permittivity,and further studies the whole electromagnetic radiation of rock Characteristics have certain significance.