Study on cause of low production and countermeasures of increasing production technology about coalbed methane wells in Shizhuang South Block

One of the keys to reduce blind investment and improve gas production efficiency is to accurately determine the causes for low production of CBM vertical wells and proposetargeted technical measures to increase production.This article takes the Shizhuang south block as the research object，and analyzes the reasons of low-yield of CBM from four aspects:geological and coal reservoir conditions，drilling technology，fracturing technology and drainage work system.On this basis，the corresponding technical countermeasures for reasons of the different low gas production were putted forward by means of acid decontamination experiment，optimized simulation of fraction parameters，analysis on the process principle of solving powder blockage and increasing production principle of reducing pump depth.The results showed that:low-yield wells due to serious drilling pollution can be improved in gas production by using acid decontamination and conventional hydraulic fracturing.The coal body structure is mainly composed of primary structure fragmented coal，and low-production CBM wells caused by unreasonable fracturing parameters are preferred to be repeated fracturing technology； low-yield wells with mainly coal or militic coal in the structure of the coal body need to determine the feasibility of top/bottom fracturing according to the top/bottom lithology and surrounding rock recharge；If the pump is more than 5 m above the coal seam and the low-yield wells has a relatively high gas production before，the gas production can be increased by deepening the pump hanging； the low-productivity wells that are sensitive to production and recovery are optimized for the secondary fracturing pump injection parameters to achieve the purpose of fracture turning.If low-yield wells caused by coal blockage，low pump efficiency in wellbore are preferred to use circulation washing device such as flushing pump to improve pump efficiency and realize normal liquid production to improve gas production.Nitrogen solution technology is preferred for increasing production in low-yield wells where the amount of water and gas production decreases dramatically by coal seam blockage near wellbore.The application of part of the on-site production increasing technology verified the reliability of the theoretical analysis.The research results provide a reference for the design of the secondary reconstruction scheme of the low-production coalbed methane well area.