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本文采用电子计算机X射线断层扫描技术(Computed Tomography),研究了龙马溪页岩在不同流体浸泡条件下,不同时刻微观结构的变化情况.实验表明流体沿微裂隙不断侵入导致的裂缝扩展、贯通是井壁失稳的主要原因.页岩裂缝产生具有明显的方向性和瞬时性,裂缝主要产生于与流体接触的前2h之内,且方向平行于层理面.不同流体浸泡条件下页岩内部变化具有明显的差异,去离子水条件下裂缝产生最多最快,KCl-聚合物钻井液次之,SM-Shal eDrill和油基钻井液浸泡下无明显变化.实验发现对于与流体接触后新产生的裂缝,其宽度基本维持恒定不变,不再随时间发生变化.而页岩中已经存在的微裂隙,其宽度在与流体接触后有一个明显的增大过程.
In this paper, the computer tomography (Computed Tomography) was used to study the microstructure changes of the Longmaxi shale under different fluid immersion conditions at different time.Experiments show that the fractures of the fluid extend along the micro-fractures, The main reason for the instability of the borehole wall is that shale fractures are obviously directional and transient, and the fractures are mainly generated within the first 2 h of contact with the fluid and oriented parallel to the bedding plane. There was a significant difference between the two groups, the cracks were the most and the fastest in deionized water, followed by KCl-polymer drilling fluid, SM-Shal eDrill and oil-based drilling fluid without significant changes.Experiments found that after contact with fluid new generation The width of the cracks in the shale is almost constant and no longer changes with time, while the existing micro-cracks in the shale have a significant increase in their width after contact with the fluid.