顶替速度对粘砂套管水泥环胶结强度影响研究

套管粘砂增加了管壁的粗糙度,造成部分钻井液滞留在砂粒间无法顶替,降低了水泥浆的顶替效率和粘砂套管的胶结强度。通过分析幂律水泥浆在套管-井壁环空中轴向紊流流场,计算粘砂套管水泥浆的顶替效率,并在此基础上建立考虑钻井液滞留的粘砂套管胶结强度计算模型。研究结果表明:随着水泥浆顶替速度增大,粘砂套管顶替效率逐渐增大,顶替速度为2.9m/s时,粘砂套管胶结强度达到最大值;粘砂套管破坏位置主要发生在胶结剂-砂粒界面,砂粒粒径4～6mm和6～8mm粘砂套管的胶结强度分别为1.509MPa和2.480MPa。

Effect of Displacement velocity to cementing strength of adhering sand casing cement-sheath

Abstract] Casing by adhering sand increases the roughness of casing wall. Meanwhile, it makes part of drilling fluid retain in sand and cannot be displaced, then reduces the displacement efficiency of cement paste and the cement strength of adhering sand casing. This article calculates the displacement efficiency of cement paste of adhering sand casing by analyzing axial turbulent flow field of power law fluid in casing-annular space. And on this basis, establish the computation model of cementing strength of adhering sand casing which take into account retention of drill fluid. Research result shows that as the displacement velocity of cement paste increases, the displacement efficiency of adhering sand casing and the cement strength increase gradually. It keeps constant after reaching the strength of cementing agent.