Research On Geophysical Response Of Coal And Their Gas Bearing

Use geophysical techniques for CBM (gas) exploration is still in exploration stage.Strengthen basic research,active conduct ultrasonic physical test, achieve breakthroughs in key for chinese CBM exploration, forming the development geophysical technique of geological condition for chinese CBM exploration is the main research tendency.Test lithology and property of rich gas and not rich gas seam, and the response relation between these physical properties and logging curves,characteristics of seismic wave field is an important content. for CBM petrophysical study.This paper,by elasticity test under room temperature,room pressure and geophysical well logging experiment in field of coal sample,coal core,and statistical analysis,studied p-wave and s-wave velocity characteristic,attenuation characteristic,azimuth anisotropic characteristic,elastic and the influence of coal metamorphic on elastic;studied the relationship between coal quality(moisture,ash,volatile),porosity,containing such geological parameters and density,velocity,resistivity such physical parameters, Through the research on relationship between measured gas content of 22 wells for Dacheng coal mine,fill 7 well for Guqiao coal mine,8 wells for Xiahuangyan coal mine and logging parameters,found the sensitive logging parameters of influence gas content,established the mines gas content forecasting model.studied structural evolution,coal seam development characteristic and the gas preservation conditions of Dacheng,used wells post-stack seismic joint inversion,forcasted the gas distuibution of no.3,no.6 coal seam in Dacheng.By study and analysis concluded:(1)Through six different coal metamorphic grade of elastic concluded that,â‘ the p-wave velocity, coal s-wave velocities and apparent density are related, and along the direction and tendency and coal seam coal layer in the direction of vertical Daniel; gradually reduce p-wave velocity S-wave velocities in vertical direction and tendency and upward does not exist the same changes relationship, performance regularity poorer; The same direction of coal and rock with p-wave velocity shear rate exists good linear correlation, but the same propagation direction of different polarization direction with the same direction s-wave velocities of p-wave velocity linear relationship between different s-wave velocities, explain differences existing in different directions.â‘¡the p-wave velocity, coal, poisson example bits attenuation anisotropic in vertical bedding direction parallel bedding direction, largest minimum.â‘¢the largest coal vitrinite reflectance and apparent density is relevant and poisson's ratio negative correlation, elastic modulus is relevant, and vertical and horizontal wave velocity is relevant, quality factor is related to quality factor, including the relevance of the highest.(2)Gas content and wave velocity and density, resistivity negatively correlated; Coal seam porosity and acoustic time, neutrons are related, and density negatively correlated; Coal rock moisture increases, wave velocity increasing, and neutron decrease, density increases, natural gamma ray increases, the resistivity reduce; Ash increases, the coal rock density increases, natural gamma ray increases, the resistivity reduce, acoustic time decreased; Coal rock volatile increases, density increases, natural gamma ray increases, the resistivity increases, wave velocity increased.(3)Through the establishment of coal physical parameter prediction mathematical relation model of geological parameters, and to verify this model, the error is lesser, results are reliable.