Cementing technology used for protecting coal reservoir

It is very important to perform a systemic research on cementing operational parameters and its influence upon the coal-bed gas exploitation,because the cased-hole completion is the main well completion method for coal-bed gas well in China.Based on the brief review of cementing operation cases and the current research of coal-bed gas well,this paper analyzed the requirements of cementing quality and protection the coal reservoir.It tabled a proposal of the slurry and operation design method combining with the experiments and operations.The isolation of coal reservoir roof is the most crucial requirement in coal-bed well cementing and the most important challenge of operational safety was preventing the lost circulation.Considered the requirement of cementing job and protection the coal reservoir,it was proposed that the desired cementing slurry density boundary should be(1.20)-(1.60)g/cm3,at the same time,the thick cement slurry should be under the low return rate,(0.5)-0.8 m/s,in the cementing operation.The cement job quality qualification rate has reached 100% in the field application,which proves that this conclusion has be of certain applicability and be of directive meaning for coal-bed gas well cementation operation and design in future.