With high capillary pressure and large specific surface area, tight coalbed may be damaged by fluid in-vasion during drilling, completion and stimulation, which may reduce engineering technical efficiency significantly. Previously, only single working fluid damage to coal reservoir has been reported, seldom taking superimposed ef-fect of damage induced by sequential contact of working fluids with the coal reservoir into account. Collecting coal samples from coal seams of upper Permian Longtan Formation in Guxu mine, southern Sichuan coal field, we conducted compatibility experiment between fluids and the permeability damage experiments of sequential contact of drilling and completion fluids and fracturing fluids with coal samples. According to the result of the reservoir damage evaluation experiment, the damage of fracturing fluids to the reservoir is the most serious, followed by drilling and completion fluids. As shown in the result of compatibility of working fluids and sequential contact damage evaluation experiment, Guar gum fracturing fluid comes first in the terms of extent of damage, followed by ion balance fracturing fluid, active water fracturing fluid and the clean fracturing fluid in sequence. Sequential contact damage experiment can simulate the engineering practice process and provide theoretical basis for evalua-tion and optimization of drill-in-fluids which is beneficial to promote the protection of coal seam and efficient ex-ploitation of coalbed methane.%致密煤岩具有高毛管压力和比表面积大等特点，在钻井、完井和增产改造过程中，流体侵入将造成储层损害，显著降低工程技术效果。以往文献仅报道了单项工作液对煤岩储层的损害，忽视了工作液顺序接触煤岩储层损害的叠加效应。以川南煤田古叙矿区上二叠统龙潭组煤样为研究对象，开展了流体之间配伍性实验、钻井完井液与压裂液顺序接触煤样对渗透率损害实验。单项工作液储层损害评价实验结果表明，压裂液对储层的损害最严重，钻井完井液次之；工作液配伍性和顺序接触损害评价实验结果表明，与钻井完井液接触后，瓜胶压裂液损害最严重，离子平衡压裂液次之，活性水压裂液较轻，清洁压裂液最轻。顺序损害实验反映了工程实际过程，为入井流体评价和优选提供理论依据，有利于促进煤层保护和煤层气高效开发。
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