Research On Migration And Deposition Of Pulverized Coal In CBM Multi-lateral Horizontal Well

Though CBM exploration is becoming more and more popular and exploitation technology is more and more advanced,there are still many problems to be solved.One of those troubles is the large amount of pulverized coal which is produced by producing pressure drop and fluid erosion because of the fragility of coal.The pulveraized coal in the wellhole will not only cause abrasion of pump cylinder and instruments,but also lead to stuck pump for deposition of pulverized coal.For all these reasons,research on migration and deposition of pulverized coal is significant for the guidance of CBM production.This paper is supported by the project ‘The numerical simulation research of CBM under status of filter and blockage among wavy wellbore in horizontal well'.It is also based on the research of pulverized coal's output feature among CBM horizontal multilateral well and the research of transportation pattern of pulverized coal.According to the theory of multiphase flow and hydromechanics,we adapt the method of CFD and the theory of multiphase flow to carry out the research of a few factors(such as how height-length ratio,wellbore's diameter,content of pulverized coal,particle's diameter of pulverized coal,migration velocity of pulverized coal,differential pressure of production and gas production rate of CBM)would affect the migration of pulverized coal in wavy horizontal wellbore.On the other hand,the flow field changes rapidly around linkage section.We carry out the numerical simulation to study the three-phase flow motion in this linkage section.We also analyze the deposition principles of pulverized coal in this area so that we could find out the relation between those parameters and the deposition of pulverized coal.Through this method,we could propose some advices to optimize the relevant parameters.The result reveals a sequence that influence the deposition and migration motion of pulverized coal in wavy wellbore which is ranked by its magnitude of impact.The parameters rank as following: particle's diameter of pulverized coal,migration velocity of pulverized coal,content of pulverized coal,diameter of wellbore,height-length ratio of wellbore,gas production rate of CBM,differential pressure of production.The research on those deposition and migration motion of pulverized coal in linkage section shows the main branch intersection angle in vertical plane has more obvious impact than the intersection angle in horizontal plane.We also get the connection between dynamic pressure in linkage section and the flow rate of three-phase flow motion in wellbore.Those conclusions we make in this paper has certain guiding significance to field operation.