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在过去的十多年中,在压裂及不稳定地层中钻井存在一定挑战性,特别是在井眼稳定方面。若要井眼稳定,需要仔细考虑井下应力、岩石强度、孔隙压力、井眼流体压力、钻井液特性等因素。井眼稳定问题在裂缝地层中更加复杂和关键,因为与其他类型的岩石相比,需要考虑更多的因素。在裂缝地层中,岩石的楔入运动造成了井眼不稳定现象,而裂缝在井眼不稳定方面起到了很重要的作用。目前,仅有较少的关于裂缝地层稳定性及加固方法方面的研究。预防井眼不稳定常用的方法是增加钻井液密度以支撑井壁。然而,允许的泥浆密度窗口限制了可用的泥浆密度范围。加固作业能使破裂压力曲线上移,破坏压力曲线下移,从而加宽了泥浆比重窗口。在破坏压力与破裂压力之间较大的允许限度使得泥浆压力调整余量更大,保证了更加安全的钻井施工。微流量控制解决了破坏压力梯度和破裂压力梯度之间数值太接近的问题。高能激光具有较高的机械钻速;由于用额外的电缆连接到井底钻具组合,因此数据采集率高;一趟钻完成钻完井作业。它们是提高井眼稳定性的最新技术。
Drilling wells in fractured and unstable formations has been challenging for more than a decade, especially in wellbore stabilization. For borehole stability, careful consideration should be given to factors such as downhole stress, rock strength, pore pressure, wellbore fluid pressure, and drilling fluid properties. Wellbore stability problems are more complex and critical in fractured formations as more factors need to be considered than in other types of rock. In fractured formations, the wedging motion of the rock caused the borehole instability, and the fractures played a very important role in the instability of the borehole. At present, there are only a few studies on fracture formation stability and reinforcement methods. A common method of preventing borehole instability is to increase the density of the drilling fluid to support the borehole wall. However, the allowable mud density window limits the available mud density range. Reinforcement operation can make the fracture pressure curve move up, destructive pressure curve down, thus widening the window of the proportion of mud. Larger tolerances between destructive and bursting pressures allow for greater mud pressure adjustment margin, ensuring safer drilling. Microfluidic control solves the problem that the values between the failure pressure gradient and the fracture pressure gradient are too close. High-energy lasers have a high ROP; data acquisition is high due to the extra cables that are connected to the bottom hole assembly; completion and completion of one pass. They are the latest technology to improve wellbore stability.