Migration Law Of CBM And Interference Mode Of Row Between Production Wells In Rough Cleat

Given the frequent gas explosion accidents and serious environmental pollution nationwide, as a new type of clean energy, the development and utilization of the CBM has become a significant work.Because the coal and rock medium is a kind of dual-porosity structure. The cleat or fracture end-face geometry and the matrix pore structure are all extremely complex and show the fractal characteristics. The cleat or fracture network, as the main channel of the CBM migration, especially their geometrical morphology have a significant impact on the fluid migration. Therefore, proving the control mechanism of the fluid migration in rough cleat is the basic premise of the CBM potential scientific evaluation and optimization design of mining technology. This mechanism has important theoretical significance and practical value.However, the field data, the conventional test methods and the empirical relationship are often based on the statistical results of macro level which is intrinsic smooth, continuous assumption and affected by the precision and the environment specifically. This result is not conducive to the discovery of the CBM migration regularity. So we must proceed from the pore scale to understand the migration process of CBM from the aspects of mechanism. After ascertaining the micro geometry control function and the way, we can deduce the transport properties of complex pore structure by science. Recently, with the rapid development of computer technology and the mature of fractal theory, the analysis model of coupling with each other has become an important means and effective method of the exploration of CBM migration law.Combining the difficult problem of the potential evaluation of CBM, this article emphatically researched the migration law of CBM in rough cleat in pore scale by using Boltzmann repertoire which is based on the dynamic theory. Specific including:(1) We comprehensively analyzed the migration law of CBM in the composite morphology space of rough cleat based on self-affine fractal property of cleat end-face geometry. And we also proposed the fracture-permeability relationship including triple effects based on action mode and strength. The triple effects are the local asperity of the fracture end-face, the internal friction in the fluid and the external friction of the interface of flow-solid. The physical parameters for each are the local roughness factor, the hydraulic tortuosity and the surface tortuosity in large scale. In which, hydraulic tortuosity and surface tortuosity shows scale Invariant feature, but the local asperity factor has long-term stable feature. At last, we proposed the fractal fracture-permeability equation of the CBM migration in single rough cleat.(2) Combining self-affine property of cleat end-face and the fact that long-range is correlative and short-range is mismatch, we proposed the algorithm that building natural cleat. On this basis, we analyzed the migration law of CBM in mismatch composite morphology space of self-affine rough cleat. The specific characteristics are as follows: Along with cleat direction, section velocity satisfied skewed normal distribution rather than parabola model described by Poiseuille equation. The distribution of aperture in self-affine mismatch cleat space is undulation possessing periodic, this feature will increase hydraulic tortuosity of cleat flow, and then weaken the penetrating quality of cleat space. More strong is mismatch degree, more obvious is tortuous flow effect, and shows monotone increasing trend.(3) According to the steric configuration of cleat network, we simulated the drainage process of CBM based on vertical wells in pore scale and analyzed jamming mode between drainage wells. The results showed that: reservoir pressure and the distance between wells have a great importance on the drainage of CBM. The trends are as follows: the velocity of CBM in the mouth of wells and the distance between wells show monotone increasing trend. And when the distance is 7.65, aiming at current experimental model, the effects of each other are least. Reservoir pressure and the velocity also show monotone increasing trend. So, properly increasing the distance and reservoir pressure are in favor of the drainage of CBM.