大排量高泵压压裂过程中射孔段套管热应力分析

发布时间：2018-01-19 10:11

本文关键词： 射孔套管温度场热应力压裂有限元分析　出处：《西安石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：大规模体积压裂具有排量大、泵压高的特点,压裂过程中,大量低温流体注入,引起套管的温度变化,从而产生热应力,对套管的强度安全造成很大影响。因此,本文以射孔段套管为研究对象,考虑温度场与应力场的耦合作用,分析射孔段套管的力学性能。对射孔段套管热应力的研究,首先进行了射孔段套管温度场分析。根据热力学第一定律和热传递基本理论,确立了合理的边界条件,建立了射孔段套管-水泥石环-围岩的三层导热模型,通过有限元分析软件对射孔段套管-水泥石环-围岩进行了温度场分析。在温度场分析的基础上,利用ANSYS有限元协同仿真平台进行了射孔段套管-水泥石环-围岩系统温度场与应力场的耦合,得出了热应力分布结果。最后,进行了射孔段套管热应力影响因素的分析与研究,应用控制变量法,建立不同属性的有限元模型,分析了水泥石环几何特性与物理特性对射孔段套管热应力的影响。结果表明:压裂施工过程中,射孔段井筒的温度分布沿径向及环向均存在不均匀现象。套管热应力约为套管材料屈服强度的38.3%,水泥石环热应力约为水泥石环材料屈服强度的55%。最大热应力点均分布于孔眼水平轴线的两侧,若孔眼处出现微裂纹,则向横向扩展。地层的位移变化方向指向井筒中性轴,对套管有挤压作用。水泥石环厚度的增大对水泥石环本身的热应力有降低作用,却对套管热应力表现为增大趋势。因此,为了降低套管热应力,保证套管的强度安全性,在水泥石环强度安全的前提下,优选水泥石环厚度为25~30mm。水泥石环的材料属性中,弹性模量对热应力的影响最大,泊松比对热应力的影响最小。
[Abstract]:Large-scale volume fracturing has the characteristics of large displacement and high pump pressure. During fracturing, a large number of low-temperature fluids are injected into the casing, resulting in the change of casing temperature and thus the thermal stress. It has a great influence on the strength safety of casing. Therefore, the coupling effect of temperature field and stress field is considered in this paper. To study the thermal stress of perforated casing, the temperature field of perforated casing is analyzed firstly, according to the first law of thermodynamics and the basic theory of heat transfer. The reasonable boundary conditions are established, and the three-layer heat conduction model of perforated section casing, cement stone ring and surrounding rock is established. Through the finite element analysis software, the temperature field of casing, cement stone ring and surrounding rock in perforation section is analyzed, based on the analysis of temperature field. The coupling of temperature field and stress field of casing cement ring surrounding rock system in perforation section is carried out by using ANSYS finite element simulation platform. The results of thermal stress distribution are obtained. The influence factors of casing thermal stress in perforating section are analyzed and studied. The finite element model with different attributes is established by using the control variable method. The influence of the geometric and physical characteristics of cement stone ring on the thermal stress of perforated casing is analyzed. The results show that: during fracturing operation. The temperature distribution in perforating section is uneven along radial and circumferential direction. The thermal stress of casing is about 38.3% of the yield strength of casing material. The thermal stress of the cement ring is about 55% of the yield strength of the cement ring material. The maximum thermal stress points are distributed on both sides of the horizontal axis of the hole. The displacement direction of the formation is directed to the neutral axis of the wellbore and the casing is extruded. The increase of the thickness of the cement stone ring can reduce the thermal stress of the cement stone ring itself. Therefore, in order to reduce the casing thermal stress and ensure the safety of casing strength, under the premise of cement stone ring strength safety. The thickness of cement stone ring is 25 ~ 30mm. among the properties of cement stone ring, elastic modulus has the greatest influence on thermal stress, and Poisson's ratio has the least effect on thermal stress.
【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】：TE357;TE931.2

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