【作者】 王秀文；

【导师】 刘巨保；

【作者基本信息】 东北石油大学 ， 固体力学， 2011， 硕士

【摘要】 固井过程中套管串在不同阶段承受不同的载荷,如何系统的研究复杂井况对套管受力状态的影响,这对于预防或减少套管发生损坏具有重要意义。本文针对固井过程中套管串的实际结构和受力状态,选取井口到井底的整体套管串为研究对象,考虑水泥浆凝固时不同阶段的套管串结构变化、力和位移边界变化,建立了固井套管串有限元分析模型,依据固井工艺推导了水泥浆凝固期间对套管串的作用力计算公式,并给出了其它外载荷公式及套管串强度校核方法。采用间隙元模拟套管串与井壁接触摩擦状态,将套管串梁单元与间隙元理论相结合,建立了固井套管串非线性静力学分析的有限单元法。采用delphi语言开发了“深井固井套管串力学分析”软件,计算了不同工况下套管串的受力状态,得到了不同因素对套管串受力状态的影响规律:井口及水泥面处轴向力在候凝期间增加的幅度随封固段长度的增加而呈非线性增大;套管串自由段的轴向力随着井口试压压力的增加而呈线性增加,平均增幅为4.7t/10MPa,且与封固段长度无关;井口及水泥面处轴向力随着回缩量的增加而呈线性降低,且数值随着封固段长度的增加而增大,本文计算出的井口回缩量比经典公式计算出的数值偏大,为现场完井时下放回缩距确定提供了理论依据。经现场3口井应用表明:不同工况下三口井套管串均满足抗拉、抗内压以及抗外挤强度条件,套管串没有发生失效;在整个侯凝过程中,三口井的井口轴向力分别增加了10t、5t、11t左右,与现场试测试结果相比,其符合率分别为98%、100%、98%,验证了计算方法和软件的正确性。针对固井过程中水泥浆未凝固时套管串失稳变形现象,选取井眼内轴向零点以下套管串为研究对象,考虑套管串变截面结构及其与井壁的接触状态,依据套管串失稳波形,按照一定的计算方法给出套管串的初始位移,并采用大位移和接触非线性分析方法模拟套管串与井壁间的接触摩擦,为套管串后屈曲分析提供了一种计算方法。更多还原

【Abstract】 In cementing process, casing string bears different loads in different time, it is very important to prevent or reduce casing failure by studying the impact of complex well conditions on the force statement of casing string.According to casing string actual structure and force statement, Select the whole casing string as research object. Build the casing string mechanical model with considering the variable of structure with casing string, force and displacement boundary change during solidification, and the force calculation formula for casing string during solidification and other external load formula and strength checking method are given.The gap element is adopted to simulate the contact condition between casing string and wellbore, nonlinear statics analysis of finite element method for casing string is set up. The software of“Mechanics analysis for casing strings in deep well cementing”is developed by delphi language, which can compute the force statement in different working conditions. Obtain the relationship between different factors and mechanics analysis: The axial force of the wellhead and cement surface presents nonlinear increase with the increasing of cementing length; The axial force of the free section of casing strings presents linear increase with the testing pressure of wellhead , the average value is 4.7t/10MPa; The axial force of the wellhead and cement surface present linear reduces with the increasing of the retraction, and the value gradually increases with the increase of cementing length.The retraction value calculated in this article is larger than what is got from the classic formulas, so it has guiding significance to determine the retraction. Application shows: three Wells meet the strength requirement in different working conditions, and the axial force respectively has increased 10t, 5t, 11t during solidification. The fore coincidence rate compared with field test is 98%, 100%, 98%. It verifies the correctness of the theoretical methods and the software.In order to sovle the instability phenomenon about casing in cementing, select the casing string that below zero axial as object in well, considering the contact about the casing with wellbore and the variable cross-section of structure, the casing post-buckling and contact with wellbore are sloved by using nonlinear method of large displacement and contact, the initial displacement of casing is obtained from the structure stability analysis, this method can be used in the post-buckling of casing string.更多还原