發(fā)布時間：2018-05-15 10:17

  本文選題：偏心公轉(zhuǎn) + 剪切紊流　； 參考：《東北石油大學》2017年博士論文

【摘要】：剪切旋流振動固井技術通過循環(huán)固井液帶動井下偏心葉柵固井工具旋轉(zhuǎn),使得套管繞井眼軸線高速偏心公轉(zhuǎn),對環(huán)空流體產(chǎn)生強烈的攪動作用,使其處于剪切紊流狀態(tài)。關于偏心環(huán)空流動問題的研究人們已經(jīng)做了大量工作,研究的流動類型包括偏心環(huán)空Poiseuille流、Couette流、螺旋流和內(nèi)管做行星運動的環(huán)空中流體的流動,而對于內(nèi)管偏心公轉(zhuǎn)條件下環(huán)空剪切紊流的研究尚未開展,該條件下環(huán)空剪切紊流提高機理固井質(zhì)量尚不明確,并且偏心公轉(zhuǎn)條件下環(huán)空剪切紊流流場對井壁和套管柱振動穩(wěn)定性產(chǎn)生不利影響,危害振動固井安全。針對以上問題,本文進行了基于套管偏心公轉(zhuǎn)環(huán)空剪切紊流提高固井質(zhì)量研究。根據(jù)慣性直角坐標和運動直角坐標以及直角坐標和雙極坐標的轉(zhuǎn)化關系,基于時間平均法并采用k-ε紊流模型,建立了運動雙極坐標系下基于套管偏心公轉(zhuǎn)環(huán)空剪切紊流的數(shù)學模型,并推導了考慮壁面粗糙度影響的壁面剪應力計算公式。采用有限體積法對該數(shù)學模型進行求解,得到了環(huán)空剪切紊流特性參數(shù)的分布,提出了表征流體不穩(wěn)定性的數(shù)學模型及其形成條件。在此基礎上分析了套管偏心公轉(zhuǎn)作用下固井質(zhì)量的提高機理,一方面,基于泥沙起動理論,提出了泥餅活化機理,考慮密實度、流體粘性和壓差的影響建立了泥餅活化的臨界剪應力模型,計算并分析了套管偏心公轉(zhuǎn)條件下環(huán)空壁面剪應力對泥餅的影響;另一方面,通過室內(nèi)試驗研究了振動對鉆井液和水泥漿靜切力的影響,分析了流體性能改善提高固井質(zhì)量的機理,并通過建立套管偏心距計算模型得到了井下偏心葉柵的作用距離,即性能改善的流體范圍。此外,建立了考慮振動壓力影響的井周應力計算模型,改進紊流摩擦耦合并考慮泊松耦合,建立了以振動壓力為驅(qū)動的套管耦合振動模型,以保證固井安全為目標優(yōu)化了固井施工參數(shù)和井下偏心葉柵結(jié)構(gòu)參數(shù)以及套管柱結(jié)構(gòu)。本文通過建立運動雙極坐標系下基于套管偏心公轉(zhuǎn)環(huán)空剪切紊流的數(shù)學模型,豐富了偏心環(huán)空流動問題的研究,完善了其提高固井質(zhì)量機理,優(yōu)化了固井施工參數(shù)和井下偏心葉柵結(jié)構(gòu)參數(shù)以及套管柱結(jié)構(gòu),為振動固井的優(yōu)化設計提供了理論依據(jù)。
[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.
【學位授予單位】：東北石油大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TE256

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本文編號：1892050