Experimental Study Of Physicochemical Reconstruction On Tectonic Coal Reservoir And Its Mechanism

Since the commercial development of coalbed methane?CBM?was achieved at Liujia block,Fuxin basin in 2003,main coal bearing basins have invested a lot of human and financial resources for exploration and development practice and theoretical research of CBM.Due to several times and additive effect of geological structure in most coal basin,tectonic coal is widely distributed in China,which not only results in weak mechanical properties of the reservoir,but also destroyed the gas migration channel in the reservoir.Therefore,the exist of tectonic coal has disadvantages to enhancing reconstruction and water-discharging and pressure-dropping.Traditional hydraulic reinforcement measures are limited.This paper took different damage degree of lean coal from Huoerxinhe coalmine in Changzhi,Shanxi province as the research object.Using THF and CS₂ solvents,the small molecule phase in coal has dissolved.Combined with the modern testing technology,the differences of chemical composition,crystal structure,porosity,diffusion and surface properties of coal samples before and after solvent reconstruction were compared and analyzed.The results show that:?1?the extraction is mainly composed of small molecule compounds which have similar molecular structure with the organic solvents.The tectonic coal includes high content of hydrocarbons and heteroatom compounds after strong tectonic effect.Then it lead to high extraction yield of organic solvent;?2?The number of pores increase in various stage after solvents reconstruction in coal.Meanwhile there are lots of open pores and strong expanding pore effect,which is in favor of gas desorption and diffusion;?3?After the effect of organic solvents,the surface tension of coal decrease,and then coal's affinity of water and CH₄ decrease.Then it results in reduced adsorption capacity.With the destruction of coal body structure increasing,the surface feature and gas molecular diffusion show a complex change in coal.But the ability of gas diffusion in tectonic coal has improved significantly after reconstruction of organic solvents.Further based on the experiments analysis of physicochemical reconstruction on tectonic coal reservoir,the mechanism of physicochemical reconstruction of organic solvents was discussed.Meanwhile comparison of the characteristics of traditional and acid fracturing fluid,the adaptability of fracturing fluid with organic solvent was analyzed.It will rich theories of coal reservoir reinforcement and reconstruction,and provide a reference for the exploration and development of coalbed methane in the area with similar geological background.