| As the oil and gas exploration and mining is more and more to develop in the direction of deep and complex reservoirs,though coalbed methane resource is rich in China,because of coal containing gas reservoir with low permeability,low pressure and low gas saturation of the "three low" characteristics,according to the needs of practical engineering application,this paper introduces hydraulic cavitation jet technology to coal-bed methane projects to improve the low permeability of coal bed methane production.Cavitation technology main principle is to use an empty chemical has the purpose of producing a large number of cavitation bubble,use of empty bubble breaking,and of the great energy released when accompanied by acoustic vibration,impact pressure and temperature effect of the original structure to the destruction of the strong coal reservoir,open the permeability of coal seam fracture increase,promote the full circulation of coalbed methane(CBM),thus improve coalbed methane production.The core of this technology is the design of hydraulic cavitation nozzle.The content of this paper is mainly divided into the basic concept of hydraulic cavitation technology and its development status,the stimulation mechanism of coal bed methane air chemical tool,the design of air chemical tool,the numerical simulation and experiment of air chemical tool.First of all,the concept of hydraulic cavitation technology and introduces the current situation of the development,as a kind of precious and CBM reserve vast non-renewable energy,the development has experienced dozens of years,people also have relatively mature development technology,such as hydraulic fracturing,thermal stimulation,multi-branch horizontal Wells,etc.,but because more than their respective application limits and the "three low" characteristics of coal seam in our country,our country’s coal bed methane production compared with the developed countries are still in a lower level,thus put forward using hydraulic cavitation technology to apply in coalbed methane production.Secondly,this paper introduces the mechanism of CBM empty hydraulic tools production,mainly includes the hydraulic cavitation bubble dynamics principle,model,and the principles of empty into for the coalbed methane production,makes us more understand the nature of cavitation phenomenon and applied to the feasibility of the coalbed methane production,and for the design of air tools,the theoretical basis for numerical simulation and experiment.Finally,numerical simulation and experiment are carried out to optimize the structure parameters and operation parameters of the self-excited oscillation type air chemical tool.The ICEM CFD was used to establish the geometric model of the cavitation tool and to partition the grid.After that,the appropriate calculation method was selected in Fluent to calculate the model with different proportions,and the cavitation experiment platform was established to carry out the cavitation experiment and the coal sample desorption experiment.The results show that the numerical simulation results are basically consistent with the experimental results,and the optimization range of the parameters of the oscillation cavity is as follows:Dc/d1=8.0～16.0,d2/d1=1.5,Lc/Dc=0.7～0.9,α1=45°～180°,V=25m/s,and confining pressure should be avoided as far as possible. |
