水平井偏心环空稳定顶替界面形状研究

Research on interface shape of steady-state displacement in eccentric annulus of horizontal well

固井顶替界面反映了顶替流体的掺混程度,降低顶替界面长度能够有效提高顶替效果和环空封固质量。由于水平井顶替剖面上密度差引起的驱动力与流体微元所在位置有关,即使稳定顶替的条件下,顶替界面也会由于驱动力的差异而产生局部凸进,使得顶替界面长度增加。文中考虑了水平井水泥浆与钻井液的密度差引起的驱动力沿周向角和半径的变化,采用二维Hele-Shaw顶替模型及微扰法理论,建立了水平井偏心环空稳定顶替界面形状描述模型,分析了水平井偏心环空顶替界面长度随密度差的变化规律,从而为设计合理的水泥浆与钻井液密度以降低水平井偏心环空稳定顶替界面长度提供理论依据。

The interface shape of cementing displacement reflects the intermixing extent of two-phase fluids and decreasing the length of displacement interface will be helpful to improve the displacement effect and annular cementing quality. Due to the change of driving force caused by the density difference between slurry and drilling fluid with the position of fluid microelement on the displacing profiles in horizontal well, the local advance of displacing interface will happen even in a steady-state displacement. As a result, the length of displacing interface will be increasing gradually. In this paper, a calculation model that describes the interface shape of steady-state displacement has been derived through considering the change of driving force with annular circumferential angle and radius and using the two-dimension Hele-Shaw displacement model and perturbation theory. Besides, it analyzes the change of interface length with density difference in the horizontal well with eccentric casing, which provides an important basis for designing slurry and drilling fluid density and decreasing the length of displacement interface.