鄂尔多斯盆地致密气水平井固井顶替效率影响因素

Increasing displacement efficiency during tight-gas horizontal-well cementing via numerical simulation

鄂尔多斯盆地致密气水平井钻井进入了快速发展阶段,钻井数量逐渐增多,水平井固井中的顶替效率低下问题也越来越凸显。为了提高水平井固井质量,掌握不同因素对固井顶替效率的影响规律,利用数值模拟的方法开展了研究,分别研究了偏心度、顶替速率、钻井液密度、流体性能对顶替效率的影响规律,确定最有利于顶替的参数值,达到提高致密气水平井固井质量的目的。研究结果表明:(1)偏心度为0.2时,顶替效率达到96.7%,基本为最大顶替效率。(2)采取低速顶替时,建议控制在0.6 m^(3)/min以内;采取高速顶替时,建议控制在1.6 m^(3)/min以上,此种情况下顶替效率最高。(3)水泥浆和钻井液的密度差控制在0.7 g/cm^(3)左右时,顶替效率最佳。(4)增大流体动切力、稠度系数及流性指数也可提高流体顶替效率。

In Ordos Basin,the tight-gas horizontal-well drilling steps into a stage of fast development and its number increases gradually.However,a displacement efficiency during horizontal-well cementing is low,which becomes more seriously.In order to improve cementing quality,the influence of different factors on the displacement efficiency were numerically simulated,and the laws of eccentricity,displacement rate,and drilling-fluid density and property affecting this efficiency were summarized.Results show that(1)the displacement effect is the best when the eccentricity is about 0.2;(2)when two displacements are respectively at lower rate below 0.6 m^(3)/min and higher rate above 1.6 m^(3)/min,the efficiency is the highest;(3)when the density difference between slurry and drilling fluid is about 0.7 g/cm^(3),the displacement efficiency is optimal;and(4)increasing the fluid yield stress,consistency coefficient,and liquidity index is also conducive to improving the displacement efficiency.