Shale gas production after drill-in, completion, and hydraulic fracturing is strongly affected by formation damage. In order to determine the damage mechanisms for nonmarine shale reservoir, a series of assessments of sensitivity damage, water block damage, water-based drill-in fluids damage, and water damage to gas diffusion on 20 shale samples obtained from Chang 7 Formation were conducted and analyzed. Results indicate that, in the Chang 7 Formation shale, there is extremely strong stress sensitivity and moderately weak water sensitivity damage. Although the liquid phase invasion depth is shallow and the water block damage is limited, the liquid phase and solid particles would enter the microfractures in the reservoir.The P-1 water-based drill-in fluid is compatible with the Chang 7 Formation shale reservoir which can meet the requirement of Chang 7 Formation shale damage controlling, the effect of water-based drill-in fluid on wellbore stability should be paid more attention. The diffusion coefficient of the shale decreases with the presence of water.A systematic damage evaluation method of working fluid considering the multi-mechanism and multi-scale mass transfer process of shale gas is needed to establish.

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一种预测页岩地层水基钻井液损伤的实验室方法

钻进、完井和水力压裂后的页岩气产量受地层损伤的影响很大。为确定非海相页岩储层的损害机制，对长7组20份页岩样品进行了敏感性损害、水堵损害、水基钻井液损害、水对气体扩散的损害等一系列评估。并进行了分析。结果表明，长7组页岩应力敏感性极强，水敏性损害中等。虽然液相侵入深度浅，水堵破坏有限，但液相和固体颗粒会进入储层的微裂缝。P-1水基钻井液与长7组页岩油藏兼容，满足长7组页岩损害控制的要求，应重视水基钻井液对井筒稳定性的影响注意力。页岩的扩散系数随着水的存在而降低。需要建立一种考虑页岩气多机制、多尺度传质过程的系统工质损伤评价方法。