大斜度井保持井眼清洁的有效方法

An effective method for borehole cleaning in high-inclination drilling

大斜度钻井过程中,钻屑在40～60°井段易堆积形成岩屑床,对井下安全危害极大,容易引发憋钻和卡钻事故。解决大斜度钻井中岩屑床的堆积,不应只考虑清除钻屑的问题,重要的是如何清除井眼低端的钻屑沉积床。进行钻井排量设计时经常使用不合理或不完整的数学模型以及使用高粘度的钻井液清洁井眼,使清洁井眼工作变得更加困难。而使用重塞钻井液可有效地破坏已形成的岩屑床。“重塞”在环空中可产生异乎寻常的“射流”把钻屑由井眼低端驱走,并且加重的钻井液可以产生更高的浮力,也有助于驱动井眼中的钻屑和淤泥。提出了重塞钻井液的设计方案,并提出了相应的建议。

In high-inclination drilling, cuttings easily accumulate in the section of 40-60 °inclination angle and form cuttings beds which lead to accidents of bit bouncing and drill pipe sticking. The important issue in solving cuttings accumulating is to remove the cuttings beds which always exist in the bottom of inclination hole, not only concern the cuttings cleaning. In the past, irrational or flawed mathematic methods had been often used in drilling fluid displacement design and high viscosity drilling fluid had been employed to clean the hole, and these will cause difficulty in borehole cleaning. However, weighty mud plunger can effectively remove existed cuttings beds. Weighty mud plunger can produce strange jet flow which remove cuttings from hole bottom. In addition, weighty mud has stronger buoyancy that is useful for driving cuttings. The design alternative of weighty mud plunger drilling fluid and correspond advises have been presented in the paper.