The Research On Production-enhancingmechanisms Of Different Kind Of Hydrofracturefluid For CBM Development

The CBM is mainly storedin an adsorption form in micropore of coal reservoir,it follows the process of “desorption-diffusion-transfusion”during its output which lead to the way that ensure high and stable CBM production,i.e.increasing its desorption and diffusion quantity and improving the permeability of coal reservoir.So the strong oxidant and surfactantfracturing fluid is used to research the production-enhancing method by the way of increasing its desorption and diffusion quantity whileimproving the permeability of reservoir.The isothermal adsorptiontest,the initial methane releasing rate teat,thepermeability test,molecular structuretest,pore structuretest,capillary forcetest and cohesiontest of coal samples before and afterdisposed by strong oxidant and surfactantsolution is done.The result shows:(1)significant change take place in themacromolecular and pore structure of coal after disposed by strong oxidant,aromatic structure carbon layer spacing(d002)increased,aromatic structure carbon diameter(La)decreased,specific surface area of pore decreased generally which lower the adsorbing methane ability of coal reservoir and promote the desorption;meanwhile the pore volume and porosity of coal increased and the permeabilityof reservoir improved due to the corrosionfunction of strong oxidant,thecapillary force of pore decreased to some extent,finally the goal of enhancing gas production is implemented.(2)The surfactantfracturing fluidwith better production-enhancing effect,which has lower capillary forceand better,is selected.The lower capillary force is able to improve thepermeability of reservoir and the better wettability can enhance the cohesion among the coal powder which make it easier to be set and fixed for coal power.Finally the water blockand velocity sensitivity is prevented to some extent and the gas production is improved.(3)Remarkable production-enhancing effect ofsurfactantfracturing fluid is obtained in Wulihou field and the gas output reached to more than 1000m3/d which indicate that this kind of fracturing fluid has a better application prospect.