大斜度井偏心环空注水泥顶替数值模拟研究

为了进一步了解大斜度井注水泥顶替机理,提高注水泥顶替效率,借助计算流体力学软件Fluent,建立了大斜度井环空三维模型,采用流体体积法进行了水泥浆顶替钻井液的数值模拟研究。分析了井斜角、偏心度以及水泥浆与钻井液的密度差对顶替效率和顶替界面稳定性的影响规律:增大井斜角会降低注水泥顶替效率;在大斜度井偏心环空中,随着水泥浆与钻井液密度差的增大,顶替效率先增大后降低;在大斜度井中,套管偏心并不完全是降低顶替效率,当套管具有一定偏心(建议偏心度取为0.1～0.2)时,可在一定程度上阻止由于正密度差造成的水泥浆在环空低侧窄间隙突进,从而提高顶替效率。通过数值模拟,总结了大斜度井与直井注水泥顶替机理的区别,为大斜度井注水泥顶替参数设计提供了一定的参考和理论依据。

Numerical Simulation of Cement Displacement in Eccentric Annulus at Highly Deviated Wells

In order to understand the displacement mechanism and improve displacement efficiency in highly deviated well,three-dimensional annular model was developed using the CFD software Fluent,and numerical simulation studied with drilling fluid displaced by cement slurry by means of VOF method.The paper studied the influences of deviation angle,casing eccentricity and density difference between cement slurry and drilling mud on displacement efficiency and stability of displacement interface.The simulation results indicated that wellbores with a high deviation angle have lower displacement efficiency;in an eccentric annulus at highly deviated section,the displacement efficiency first increases then decreases with the increase of density difference between cement slurry and drilling fluid;casing eccentricity is not absolutely a factor reducing displacement efficiency in highly deviated well.A certain casing eccentricity(eccentricity 0.1-0.2 proposed) can eliminate fingering caused by the density difference to some extent in narrow annulus at lower side,and improve displacement efficiency.After numerical simulation study on cement displacement,the displacement mechanism differences between highly deviated wells and vertical wells were identified,which provides reference and basis for optimizing displacement parameters in the design of cementing for highly deviated wells.