【作者】 牟艳宇；

【导师】 艾池；

【作者基本信息】 东北石油大学 ， 油气井工程， 2011， 硕士

【摘要】 造斜段岩屑在重力作用下易沉积下井壁形成岩屑床,岩屑床的存在给钻井施工带来诸多安全问题,这些问题包括:高摩阻和扭矩、卡钻、憋泵、粘附卡钻、不能有效将钻压传至钻头、不能解释井的方向变化、钻井液漏入产层而影响最终采收率、钻进缓慢甚至阻塞井眼造成井眼报废。所以,造斜段岩屑运移是保证钻井施工安全及提高固井质量的关键。造斜段由于井眼弯曲的影响,钻具偏向下井壁,钻具旋转改变了环空宽窄间隙处的流场分布,增大了环空钻井液的紊流度,使处于岩屑床表面的岩屑被搅动起来,随着钻具旋转的方向运移,将其带到环空高流速区,增大了岩屑被上返的钻井液带到井口的概率。因此,研究钻具旋转对造斜段岩屑运移的影响对携岩理论及工程实际有着重要的意义。本文通过对环空流体力学分析建立了考虑钻柱旋转作用下环空流场的周向速度分布模型;通过固-液两相流理论对岩屑颗粒进行受力分析,根据岩屑运移的启动条件及悬浮条件分别建立考虑钻具旋转影响的岩屑颗粒翻滚、上升、滑移和悬浮的临界启动速度模型,分析钻具旋转对岩屑临界启动速度的影响规律,通过计算发现:在150RPM下,宽间隙处最大影响率为38%,窄间隙处最大影响率为47%;最后根据岩屑临界启动速度模型,考虑钻具旋转作用对偏心环空不同间隙处岩屑启动与运移规律的影响,真实的描述了岩屑在环空中不同位置处的运动状态,提出了评价井眼清洗效果的新方法。更多还原

【Abstract】 The curve section cuttings are easier to deposit to the down sidewall under gravity then form cuttings bed. The cuttings bed existence has brought drilling many safety problems. Those problems include that high friction and torque, bit freezing, pump choking up, adhere sticking, failing to communicate drilling pressure to drill bit, can’t explain wells direction change, drilling fluid leaking into the production formations and affect the ultimate recovery, drilling slow even jams borehole to cause borehole scrapped. Consequently, cuttings removal of building inclined section is the key point to ensure drilling security and improve cementing quality.The curve section drilling tools turn to down sidewall because of borehole bending. Drilling tools rotating changes the flow field distribution of annular width gap, increase annular drilling fluid turbulence scale, and make the cuttings in bed surface stir. With the drilling tools rotating direction migration, bring cuttings to high velocity area of annular and increase the probability of the cuttings are carried to wellhead by return drilling fluid. Thus, the study on influences of the drilling tools rotating to cuttings removal in building inclined section has an important meaning for carrying cuttings theory and engineering practice.Analyzing the annulus fluid mechanics in the paper, the circumferential velocity distribution model of annulus flow field considering drillstring rotation was established. The force acting on the cuttings was analyzed by liquid-solid two phase flow theory, According to startup condition and suspension condition of cutting transport The critical startup velocity model of cuttings particles flipping, climbing, slippage and suspension. The influence of drilling tools rotating to cuttings critical startup speed is analyzed. Through calculating, we find that: At 150RPM,the biggest effect rate to the wide annular tolerance is 38%, to the narrow annular tolerance is 47%;at last,in accordance with the critical toggle speed model of rock debris ,with the effect of drill rotating function to rock debris start and migration law at different eccentric annulus,describe the cuttings motion state of different position in annular, and a new method of evaluate borehole cleaning effect is proposed.更多还原