欠尺寸稳定器环空流场特性模拟

欠尺寸稳定器在页岩气导向钻井中具有控制井眼轨迹、降低摩阻/扭矩、减少钻具阻卡的风险和改善井眼清洁
状况等多重作用，但欠尺寸螺旋稳定器作用下的环空流场特性和作用机理并不完善。为此，采用时均紊流黏性模型法和
Realizable k–ε 湍流模型，对欠尺寸螺旋稳定器环空流体流动特性进行了数值仿真模拟。模拟结果表明，在稳定器环空
入口段的环空流动较稳定，靠近稳定器位置开始出现扰动；在稳定器环空中下游（稳定器外侧和出口段）环空流速、总压
力和动压力的分布均出现了3 个轴对称的流动区域，该流动区域的形成、发展和分布规律基本呈螺旋状，这种螺旋流动
状态有利清除井壁岩屑床；而且该段流场涡量较大，流动迹线的发展也极不规律，即稳定器的螺旋结构导致流体发生绕
流，绕流时形成了大量的漩涡流动，伴随产生了较大的动压力，而动压力诱发的激振力会加剧钻柱的振动。

Numerical Simulation of Annulus Flow Field for Under-sizeStabilizer Annulus

Abstract：The under-size stabilizer have multiple functions in the steerable drilling for shale gas，which could not only control
well trajectory，but also help reduce friction/torque，reduce the risk of drilling resistance and improve hole cleaning status. While
the annulus flow characteristics and mechanism of the inadequate spiral stabilizer are not perfect. To solve these problems，we
stimulate the annulus fluid flow characteristics of the inadequate spiral stabilizer with the turbulent viscosity model method and
Realizable k-epsilon turbulence model，and the results show that：the annulus flow around the stabilizer inlet section is more
stable，beginning to appear in flow close to the position of the stabilizer；in the stabilizer annulus downstream section（lateral
stabilizer and outlet section），the annulus velocity，total pressure and distribution of the dynamic pressure bears axis symmetry
flow respectively. The formation，development and distribution of this section are the spiral shape，which is good to clearing
borehole cuttings bed. In addition，the eddy flow amount is big and，the development of streamline is irregular，which means
the spiral structure of the stabilizer leads to the fluid flowing around. The around flow forms a large number of eddy flow，
accompanied by a greater dynamic pressure，and the induced exciting force by dynamic pressure will increase the vibration of
drill string.