To address the issue of short pump maintenance cycles caused by serious shaft scaling in coal-bed methane wells of Dacheng,a study is conducted based on the analysis of the produced water quality and scaling composition in coalbed methane wells.The results indicate that the formation water in deep coalbed methane wells is rich in HCO3-ions,which are easy to form carbonate scales with metal cations.The main components of the scale are FeCO3,iron oxide and small amounts of CaCO3,MgCO3,etc.It is identified that pressure and flow rate are the primary factors influencing scaling in coalbed methane wells.The scaling mechanism is attributed to the decrease of fluid pressure induced by drainage,leading to the precipitation of large amounts of CO2 from the water,while iron oxides are primarily produced by the cor-rosion of metal Fe by HCO3-ions.Based on the scaling mechanism and geological characteristics of coal-bed methane wells in Dacheng,a comprehensive treatment method of lining oil pipes and regular dosing is proposed to prevent scaling,which has been preliminarily validated.This provides crucial support for the efficient and stable development of deep coalbed methane reservoirs.
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