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标题：Numerical modeling of motion of displacement interface in eccentric annulus during primary cementing
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作者：Jinfei Sun ; Zaoyuan Li ; Pingya Luo 等
期刊名称：Energy Science & Engineering
电子版ISSN：2050-0505
出版年度：2020
卷号：8
期号：5
页码：1579-1591
DOI：10.1002/ese3.615
出版社：John Wiley & Sons, Ltd.
摘要：Cementing operations are of major importance to the long‐term zonal isolation and safety of oil and gas wells. As one of the well barriers, the cement sheath is key to the long‐term integrity of the wellbore. If the cement slurry does not completely fill the annulus between the casing and formation during the primary cementing displacement process, a potential leakage channel for subsurface fluids is created. In this study, the motion of the interface between the cement and other displaced fluids was examined during cementing displacement. By dividing an eccentric annulus into two 2D planes along the radial and azimuthal directions, a set of motion models of the interface were developed and solved numerically using a first‐order upwind finite‐difference method. The influences of modified density difference F * , Bingham numbers B 1 and B 2 , plastic viscosity ratio m , eccentricity e * , and diffusion coefficient D * on the motion behavior of the displacement interface were determined. The results indicated that the interface of the eccentric annulus showed serious channeling and a physical mixing phenomenon. Some residual displaced fluid could remain at the casing‐cement and cement‐formation interfaces as a result of the improper design of the fluid parameters. Keeping F * > 0 and B 2 < 5 beneficially removed residue from the displaced fluid on the wall, and increasing F * and B 1 (or decreasing B 2 , m , e * and D * ) was conducive to the smooth motion of the displacement interface. This work showed that the interface motion model could predict the displacement quality and has great potential for improving the design of the primary cementing parameters.
关键词：channeling phenomenon;displacement interface;finite‐difference method;primary cementing;wellbore integrity