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在过去的几十年中 ,许多北海钻井作业使用了水基钻井液。为优化钻屑运移及振动筛上完整的钻屑 ,需要研制一种具有高的低剪切速率黏度的抑制钻井液。但钻屑质量和井眼稳定性没有直接的联系。目前 ,在从井筒向外输送钻屑过程中 ,一种低静切力 /黏度的钻井液效果很好。因此 ,近年来通过降低高分子量聚合物的含量 ,增加低分子量聚合物的含量来提高井眼净化效果。少部分被圈闭在井筒下岩床里的钻屑被输送到地表。本文通过观察起下钻时间、下套管速度和总的钻井时间来表明低黏 /低静切力的钻井液是如何改善钻井液性能的。除了黏度方面的变化外 ,在NaCl和KCl浓度及混合物方面进行了大范围室内及现场试验。本计划目前用的是中等浓度的KCl,已经改善了井眼稳定性。在特殊地层 ,通过使用低浓度的KCl及改进油井设计 ,不稳定井眼发生的频率减少了。本文详细地解释了在钻井过程中钻井液设计是如何优化化学性能和井眼净化性能的。在最近 3年中 ,由于钻井设计的改变及水基泥浆系统的应用 ,特殊油井钻井性能得到提高 ,与早期相比 ,总的钻井时间减少了大约 5 0 %。
In the past few decades, many North Sea drilling operations have used water-based drilling fluids. In order to optimize drilling cuttings and complete cuttings on the shaker, it is necessary to develop a controlled drilling fluid with high viscosity at low shear rates. However, there is no direct correlation between cuttings quality and borehole stability. Currently, a low-cut / viscosity drilling fluid works well when drilling cuttings out of the wellbore. In recent years, therefore, the wellbore purification effect has been enhanced by reducing the content of high-molecular-weight polymers and increasing the content of low-molecular-weight polymers. A small portion of the cuttings trapped in the downhole bed is delivered to the surface. This article shows how drilling fluids with low viscous / low static forces improve drilling fluid performance by looking at drill down time, casing speed, and total drilling time. In addition to changes in viscosity, a wide range of in-room and field tests were conducted on NaCl and KCl concentrations and mixtures. The program currently uses medium concentrations of KCl, which have improved wellbore stability. In special formations, the frequency of unstable boreholes is reduced by the use of low concentrations of KCl and improved well design. This article explains in detail how drilling fluid design optimizes chemical performance and wellbore purification performance during drilling. During the last three years, drilling performance has been improved for special wells due to changes in drilling design and application of water-based mud systems, reducing total drilling time by approximately 50% compared with earlier periods.