井筒凹陷区域驱替流动特性及效率数值研究

发布时间：2018-02-26 21:08

本文关键词： 凹陷区域顶替效率数值模拟 Fluent 非牛顿流体　出处：《西安石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：在油田开发过程中,井筒存在局部凹陷现象,其发生的根本原因是地层岩性不一致和钻井技术限制所导致的局部井径扩大和井壁冲蚀。凹陷区域内的钻井液在注水泥过程中难以被驱替,造成水泥浆的顶替效率较低,最终导致固井质量较差。因此,研究井筒凹陷区域驱替流动特性及效率对提高固井质量具有重要意义。本文基于非牛顿流体力学基本原理和流体运动基本控制方程,结合相关的固井顶替理论知识,运用计算流体动力学的常用软件Fluent对井筒凹陷区域固井顶替流动的过程进行了数值模拟。分别研究了流态、密度差、浆体性能、凹陷段长度、井斜角、环空间隙对凹陷区域水泥浆顶替效率的影响,模拟结果表明:采用塞流或紊流顶替、增大水泥浆与钻井液两者之间的正密度差都有利于提高凹陷区域水泥浆的顶替效率;确定了较高的凹陷区域顶替效率对应的浆体性能(即钻井液以及水泥浆的粘度、动切力、稠度系数和流性指数);凹陷区域的顶替效率随着环空间隙的减小而降低,凹陷段长度越长则顶替效率越低,井斜角越大则顶替效率越低;此外,随着时间的增长,凹陷区域水泥浆的顶替效率值迅速升高,当顶替效率升高到一定值后增速变缓,之后其值基本不再随着时间的增长而发生变化。研究结果对提高井筒凹陷区域固井顶替效率及固井质量具有一定的指导意义,同时利于明确井筒凹陷区域顶替流动过程中的顶替机理,为注水泥设计和施工提供必要的理论依据。
[Abstract]:In the course of oilfield development, there is a phenomenon of local depression in the wellbore. The root cause of this phenomenon is the local diameter enlargement and wall erosion caused by the inconsistency of formation lithology and the limitation of drilling technology. The drilling fluid in the sag area is difficult to be dislodged in the process of cement injection, resulting in the low displacement efficiency of cement slurry. Therefore, it is important to study displacement flow characteristics and efficiency in wellbore sag area to improve cementing quality. This paper is based on the basic principles of non-Newtonian fluid mechanics and the basic governing equations of fluid motion. Combined with relevant cementing displacement theory knowledge, numerical simulation of cementing displacement flow in wellbore sag area is carried out by using common software Fluent of computational fluid dynamics. The flow state, density difference, slurry performance and length of sag section are studied respectively. The influence of well angle and annulus clearance on the displacement efficiency of cement slurry in the sag area. The simulation results show that the plug flow or turbulent displacement is used. Increasing the positive density difference between cement slurry and drilling fluid can improve the displacement efficiency of cement slurry in the sag area, and determine the slurry performance (I. E. the viscosity of drilling fluid and cement slurry, the dynamic shear force) corresponding to the higher displacement efficiency in the sag area. Consistency coefficient and fluidity index, the displacement efficiency decreases with the decrease of annulus gap, the longer the length of the sag, the lower the displacement efficiency, and the lower the displacement efficiency with the increase of the inclined angle of the well, in addition, with the increase of time, the displacement efficiency decreases with the decrease of annulus gap. The displacement efficiency of cement slurry in the sag area increases rapidly, and the increase of displacement efficiency slows down when the displacement efficiency reaches a certain value. After that, its value does not change with the increase of time. The research results have certain guiding significance for improving cementing displacement efficiency and cementing quality in wellbore sag area. At the same time, it is helpful to clarify the displacement mechanism in the displacement flow process in the wellbore sag, and to provide the necessary theoretical basis for the design and construction of cement injection.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE256

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