Research On Optimization Design Of Double-pipe Gas Lift In Coalbed Methane Well

Different from the production mechanism of conventional oil and gas,CBM wells need to use the confined water in the coal seam to reduce the pressure before production,so that the methane adsorbed in the coal seam is released.For a long time,most coalbed methane wells use rod pump or screw pump to lift liquid and gas production.The pump body often has various eccentric wear problems during the drainage and production operation,which leads to frequent pump replacement,which seriously reduces the cost of liquid and gas production.Productivity.Therefore,this thesis proposes a method of using the double-pipe gas lift process to replace the rod pump for liquid drainage and gas production,so as to ensure the long-term stable production of CBM wells.The doublepipe gas lift process is performed by running a new small-diameter tubing string into the original production tubing,and then injecting gas into the small-diameter tubing string for forward lift,or injecting gas into the annulus between the small-diameter tubing string and the tubing for reverse method of lifting.In this study,on the basis of analyzing the advantages and disadvantages of the double-pipe gas lift drainage gas recovery process in CBM wells,a mathematical model for the optimal design of double-pipe gas lift in CBM wells was established,and a series of analysis and research were carried out.Firstly,the pressure calculation model is optimized for the injection and production process of the double-pipe gas lift.On the one hand,the Cullend-Smith method is selected as the calculation model of the single-phase gas injection process,and on the other hand,the Gary model is selected as the doublepipe gas lift.The calculation model of the two-phase outflow process;secondly,the principle of double-pipe gas lift technology in coalbed methane wells is studied,compared with the common gas lift extraction technology,and the dual-node system analysis method of oil-casing-annulus air production and the oil-casing-annular gas extraction technology are proposed respectively.The three-node system analysis method for gas without air production;thirdly,the physical simulation experiment of double-pipe gas lift effect is designed and carried out,which verifies the effectiveness of double-pipe gas lift in CBM wells for liquid gas production;finally,the double-pipe gas lift in CBM wells is used The optimal design mathematical model is used to carry out the optimal design research for a coalbed methane well,and the field construction is carried out,and a good production effect is obtained.