Analysis of low production coalbed methane wells and application of secondary reconstruction technologies

Most coalbed methane reservoirs in China are of low porosity, low permeability and with extensive structural coals, which is difficult to be reformed, resulting in low single well gas production and recovery rates.It is the the key target for the development of coalbed methane industry to choose high efficiency reservoir and well reconstruction technology to effectively improve low efficiency wells.This paper systematically dissects the reasons for low production under the influence of "geological reservoir conditions, engineering construction reforms and drainage management control", summarizes the related technologies and application effects of the secondary reconstruction of coalbed methane wells, and provides suggestions for targeted reforms of different types of low-efficiency wells.The secodary reconstructable low-yield factors in coalbed methane wells include insufficient fractures propagation, fractures/pipe coal fines blockage, and limited pressure drop area.During secondary reconstruction, the distribution of coal structure, primary fracture morphology, reservoir permeability, variations of gas and water production, and applicability of drainage equipment need to be considered.The secondary reconstruction technology covers physical, chemical, microbial, and other methods.Secondary hydraulic fracturing, indirect fracturing, and anhydrous fracturing in physical methods, as well as acidification and permeability increasing technology and foam acidification in chemical methods are widely used.In secondary reconstruction, the reservoir adaptability of the reconstruction technology should be analyzed based on the geological conditions, primary reconstruction results, engineering and drainage status, and the purpose of secondary reconstruction should be determined based on the engineering drainage situation.In the secondary reconstruction, re-damage of the reservoir should be avoided to achieve effective transformation and improve the coalbed methane production from single well and well patterns.