Method and Application of Reducing Pressure and Increasing Production in Nanometer Porous Coal Seam

Objectives: In order to deeply analyze the feasibility of reducing pressure and increasing production of coalbed methane wells in nano-porous coal seams and clarify the principle of well selection. Methods: The sensitivity of bottom hole flowing pressure to coalbed methane production is analyzed by establishing productivity equation in stable production period of coalbed methane wells. Combined with the numerical simulation method, the drainage and production effect of L-1 well in the Block A is simulated after reducing the flowing pressure at the bottom of the well. Results: The results show that for CBM wells that have been put into production, the effect of increasing the production can be achieved by reducing the bottom hole flowing pressure, and when the bottom hole flowing pressure is large, reducing the bottom hole flowing pressure can obtain a larger increase in gas production. The cumulative gas production of Well L-1 can be increased by 110x104m3 compared with the previous measures, and the increase rate can reach 85%. Conclusion: Combining with the pressure-reducing and increasing production wells in the Block A, the applicable conditions for pressure-dropping and increasing production to increase the production of CBM wells are proposed, that is, continuous and stable drainage and production, and there is a certain height of liquid column between the moving liquid level and the coal roof before operation.