基于套管偏心公转环空剪切紊流提高固井质量研究

发布时间：2018-05-15 10:17

本文选题：偏心公转 + 剪切紊流　；参考：《东北石油大学》2017年博士论文

【摘要】：剪切旋流振动固井技术通过循环固井液带动井下偏心叶栅固井工具旋转,使得套管绕井眼轴线高速偏心公转,对环空流体产生强烈的搅动作用,使其处于剪切紊流状态。关于偏心环空流动问题的研究人们已经做了大量工作,研究的流动类型包括偏心环空Poiseuille流、Couette流、螺旋流和内管做行星运动的环空中流体的流动,而对于内管偏心公转条件下环空剪切紊流的研究尚未开展,该条件下环空剪切紊流提高机理固井质量尚不明确,并且偏心公转条件下环空剪切紊流流场对井壁和套管柱振动稳定性产生不利影响,危害振动固井安全。针对以上问题,本文进行了基于套管偏心公转环空剪切紊流提高固井质量研究。根据惯性直角坐标和运动直角坐标以及直角坐标和双极坐标的转化关系,基于时间平均法并采用k-ε紊流模型,建立了运动双极坐标系下基于套管偏心公转环空剪切紊流的数学模型,并推导了考虑壁面粗糙度影响的壁面剪应力计算公式。采用有限体积法对该数学模型进行求解,得到了环空剪切紊流特性参数的分布,提出了表征流体不稳定性的数学模型及其形成条件。在此基础上分析了套管偏心公转作用下固井质量的提高机理,一方面,基于泥沙起动理论,提出了泥饼活化机理,考虑密实度、流体粘性和压差的影响建立了泥饼活化的临界剪应力模型,计算并分析了套管偏心公转条件下环空壁面剪应力对泥饼的影响;另一方面,通过室内试验研究了振动对钻井液和水泥浆静切力的影响,分析了流体性能改善提高固井质量的机理,并通过建立套管偏心距计算模型得到了井下偏心叶栅的作用距离,即性能改善的流体范围。此外,建立了考虑振动压力影响的井周应力计算模型,改进紊流摩擦耦合并考虑泊松耦合,建立了以振动压力为驱动的套管耦合振动模型,以保证固井安全为目标优化了固井施工参数和井下偏心叶栅结构参数以及套管柱结构。本文通过建立运动双极坐标系下基于套管偏心公转环空剪切紊流的数学模型,丰富了偏心环空流动问题的研究,完善了其提高固井质量机理,优化了固井施工参数和井下偏心叶栅结构参数以及套管柱结构,为振动固井的优化设计提供了理论依据。
[Abstract]:Shear swirl vibration cementing technology drives downhole eccentric cascade cementing tool rotation through circulating cementing fluid, which causes the casing to rotate around the hole axis at high speed, which produces strong stirring effect on annulus fluid and makes it in shear turbulent state. A great deal of work has been done on the problem of eccentric annular flow, including the Poiseuille flow in the eccentric annulus, the helical flow and the flow in the annulus in which the inner tube moves. However, the research on annulus shear turbulence under eccentric rotation of inner tube is not carried out, and the cementing quality of annular shear turbulence under this condition is not clear. The shear turbulent flow field in annulus under eccentric rotation has adverse effects on the vibration stability of wellbore and casing string, which endangers the safety of vibration cementing. In view of the above problems, this paper studies the improvement of cementing quality based on annulus shear turbulence in casing eccentricity. According to the transformation relationship between inertial Cartesian coordinates and motion Cartesian coordinates and between Cartesian coordinates and bipolar coordinates, the k- 蔚 turbulence model is adopted based on the time averaging method. A mathematical model of shear turbulence based on the annular annulus of casing eccentricity in a moving bipolar coordinate system is established, and a formula for calculating the shear stress of a wall considering the influence of wall roughness is derived. The finite volume method is used to solve the mathematical model and the distribution of the characteristic parameters of annular shear turbulence is obtained. The mathematical model and its forming conditions are proposed to characterize the fluid instability. On the basis of this, the improvement mechanism of cementing quality under the action of casing eccentricity rotation is analyzed. On the one hand, based on the sediment starting theory, the activation mechanism of mud cake is put forward, and the compactness is considered. The critical shear stress model of mud cake activation is established by the influence of fluid viscosity and pressure difference. The influence of annulus wall shear stress on mud cake under the condition of eccentric casing rotation is calculated and analyzed. The effect of vibration on static shear force of drilling fluid and cement slurry is studied through laboratory tests. The mechanism of improving fluid performance and improving cementing quality is analyzed, and the operating distance of downhole eccentric cascade is obtained by establishing a casing eccentricity calculation model. That is, the fluid range of performance improvement. In addition, the calculation model of borehole stress considering the influence of vibration pressure is established, the turbulent friction coupling is improved and Poisson coupling is considered, and the coupling vibration model driven by vibration pressure is established. The cementing operation parameters, downhole eccentricity cascade structure parameters and casing string structure were optimized to ensure cementing safety. In this paper, a mathematical model of shearing turbulence in annular annulus based on casing eccentricity is established in a moving bipolar coordinate system, which enriches the study of eccentric annulus flow and improves the mechanism of improving cementing quality. The parameters of cementing operation, eccentric cascade structure and casing string structure are optimized, which provides a theoretical basis for the optimum design of vibration cementing.
【学位授予单位】：东北石油大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TE256

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