大斜度井段偏心环空钻井液紊流携岩规律研究

发布时间：2018-05-03 09:52

本文选题：大斜度井段 + 紊流　；参考：《东北石油大学》2015年硕士论文

【摘要】：水平井、大位移井在海洋油田、老油田和低渗透油田开发中得到了广泛应用。但在钻井过程中,当液流速度小于岩屑悬浮运移速度时,岩屑容易在大斜度井段沉降并形成岩屑床,导致钻柱高摩阻和扭矩、低机械钻速、卡钻等问题。因此,本文重点研究了大斜度井段偏心环空钻井液紊流流动、岩屑起动以及钻井液紊流携岩规律,其预测值与实验数据进行了对比,验证了模型的可靠性。采用结构网格划分环空流体域,用滑移网格模拟钻柱旋转,基于Realizable k-ε紊流模型和SIMPLE求解方法,模拟了水平井段同心、偏心和存在静止岩屑床的偏心环空钻井液紊流特性。引入4种环空当量直径计算方法,通过与实验数据对比发现,选择Slot或Lamb方法更能准确预测环空摩擦压降。考虑岩屑床面颗粒的浮重、上举力、拖拽力、液流压耗、粘着力及附加质量力,结合颗粒的随机分布函数和紊流壁面律理论,建立岩屑滑移、滚动和举升起动的力学模型。模型计算结果显示,岩屑举升起动所需钻井液排量要高于滚动,且都随岩屑床高度增大而减小,并据此估算岩屑床高度。基于欧拉固液两相流模型和钻井液Realizable k-ε紊流模型,模拟了偏心环空钻柱旋转条件下的钻井液紊流携岩规律。模拟发现钻柱旋转使得岩屑床沿旋转方向倾斜,在环空内呈非对称分布状态,并减小环空岩屑浓度和固液压降,其变化幅度受井斜角、岩屑注入浓度、岩屑直径、钻井液流速和粘度的影响,但当转速达到临界值后,其作用效果并不显著。根据数值模拟结果形成了岩屑体积浓度和固液压降经验模型。
[Abstract]:Horizontal wells and long-reach wells have been widely used in the development of offshore oil fields, old oil fields and low permeability oil fields. However, in the drilling process, when the liquid flow velocity is less than the cuttings suspended migration velocity, the cuttings are easy to settle in the large slope well section and form cuttings bed, which leads to the problems of high friction and torque of drill string, low mechanical drilling speed, and drilling jam and so on. Therefore, in this paper, the turbulent flow of eccentric annulus drilling fluid, cuttings starting and turbulent rock carrying of drilling fluid are studied. The predicted values are compared with the experimental data, and the reliability of the model is verified. The structural grid is used to divide the annulus fluid domain, and the slip mesh is used to simulate the rotation of drilling string. Based on Realizable k- 蔚 turbulence model and SIMPLE solution method, the turbulent characteristics of eccentric annulus drilling fluid in horizontal well section with concentric, eccentricity and static cuttings bed are simulated. Four methods for calculating equivalent diameter of annulus are introduced. By comparing with experimental data, it is found that Slot or Lamb method can accurately predict friction pressure drop in annulus. Considering the floating weight, upward lifting force, towing force, fluid pressure consumption, adhesion force and additional mass force of debris bed particles, combined with the random distribution function of particles and the turbulent wall law theory, a mechanical model of cuttings sliding, rolling and lifting start is established. The model results show that the amount of drilling fluid required for cuttings lifting and starting is higher than that for rolling, and both of them decrease with the height of cuttings bed increasing, and the height of cuttings bed is estimated accordingly. Based on the Euler solid-liquid two-phase flow model and the Realizable k- 蔚 turbulence model of drilling fluid, the turbulent rock carrying law of drilling fluid under the condition of eccentric annulus drilling string rotation is simulated. The simulation results show that the drilling string rotation causes the cuttings bed to incline along the rotating direction, and presents an asymmetrical distribution state in the annulus, and reduces the sawdust concentration and the solid-liquid pressure drop in the annulus. The variation amplitude is affected by the angle of the well, the cuttings injection concentration and the cuttings diameter. The effect of velocity and viscosity of drilling fluid is not significant when the speed of drilling fluid reaches the critical value. Based on the numerical simulation results, an empirical model of cuttings volume concentration and solid-liquid pressure drop is established.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE254

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