裂缝性致密砂岩气藏入井流体伤害规律

塔里木克深区块裂缝性致密砂岩储层具有埋藏深，孔隙度、渗透率低，裂缝发育，非均质性强等特征，不经过压裂增产措施难以达到工业开采价值。钻完井以及增产改造过程储层与工作液及其所携带的固体颗粒相接触，容易引起储层渗透率降低，从而导致产能降低。以人工劈缝的储层岩心为评价岩心，使用储层成像测井资料确定岩心裂缝宽度，对裂缝性致密砂岩储层钻井液/压裂液损害进行了评价。实验结果表明，在围压低于4.5 MPa的情况下，模拟裂缝岩心渗透率保持不变，模拟裂缝岩心渗透率与缝宽呈三次方关系；随着裂缝宽度的增加，压裂液伤害程度逐渐减小，但是钻井液伤害程度先增大后减小，存在一个伤害峰值；此外，一步酸可以显著提高裂缝渗透率，解除钻井液/压裂液伤害。该研究对低伤害新型工作液的研发以及储层保护措施的优化具有一定的指导意义。 

Regularities of Fractured Tight Sandstone Gas Reservoirs Damaged by Work Fluids

The fractured tight sandstone gas reservoir in Block Keshen, Tarim Basin, is deeply buried, and has those features such as low porosity and permeability, developed fractures and strong heterogeneity. The reservoir, if not stimulated by fracturing operation, is of no commercial value. Contact of the reservoir with work fluids during drilling/completion operations and stimulation process results in reduction in formation permeability because of the invasion of the solid particles in the fluids into the formation, thereby causing decrease in the productivity of the reservoir. In laboratory experiments, reservoir cores with artifcial fractures were used to evaluate reservoir damage caused by drilling/fracturing fluids, and the width of the fractures was determined by imaging logging data of the reservoir. Experimental results showed that when the confning pressure was less than 4.5 MPa, the permeability of the cores with artifcial fractures, which has cubic relation with fracture width, remained constant. As the width of the fractures increased, the permeability damage caused by fracturing fluid decreased. However, permeability damage caused by drilling fluid frst increased and then decreased when the fracture width was increasing, showing a peak value of permeability damage. Furthermore, acid can be used to remarkably increase the permeability of the fractures, thereby removing damage caused by drilling/fracturing fluids. This study is useful in guiding the development of new low damaging work fluids and the optimization of reservoir protection measures.