Experimental Study On Physical And Mechanical Properties Of Coal Specimens Modified By Organic/Acid Complex Solution

In order to discuss the effect of organic/acid composite solution on the physical and mechanical properties of coal,mercury intrusion,wetting angle test,expansion test,mechanical properties test,powder X-ray diffraction,infrared spectroscopy and other means are used to characterizate the pore structure,wetting angle,swelling rate and uniaxial compressive strength of the organic/acid composite solution at different temperatures.The mechanical properties of coal are analyzed by temperature.Based on the meso-damage theory and the macroscopic statistical damage model,the constitutive equation of coal uniaxial failure after the formation of organic/acid complex solution was established.The microcosmic mechanism of organic/acid composite solution modified coal was analyzed Main results are as follows:(1)After soured by organic/acid complex solution,the pore space in the coal increases.As the soaking temperature increases,the coal porosity gradually increases.The wetting angle of water-coal decreases with increase of the temperature of the organic/acid compound solution and wettability gradually increased.The coal sample volume expands,and the expansion process is divided into four stages:the stage of expansion strain rate increase,the stage of expansion strain rate stabilization,the stage of expansion strain rate decay and the stage of stable expansion.(2)The change of microscopic pore structure of coal sample and the expansion and deformation caused the change of macroscopic mechanical properties.With the increase of immersion temperature,the internal pore fissures gradually develop,the longitudinal wave velocity decreases gradually,and the increase of damage leads to the decrease of elastic modulus,shear modulus,uniaxial compressive strength and impact energy index.(3)The dissolution of carbonate minerals is mainly due to the strong charge adsorption on the surface of the mineral with positively charged and anionic surfactants,And the organic/acid complex solution redox reacts with the carbonate minerals.The change of microscopic pore structure of coal sample is mainly due to the change of mineral content.Thus visible,organic/acid complex solutions can react chemically with minerals in coal.The micro-pore structure of coal is changed,and the macro-mechanical properties of coal is changed.Research results provide the experimental basis for the chemical method in the transformation of coal reservoirs.