Abstract:

A computational mechanics model for designing pre-stressed inner or outer insulation tubes with optimum expansion rate was built up according to their characteristics of the force load and deformation during different courses of manufacture, running in and steam injection. Calculating equations of the maximum expansion rate, minimum expansion rate and proportional expansion rate of the insulation tube at well head or well-bottom packers were deduced based on this mechanics model. A software compiled by the Visual Basic computer language was applied to calculate the optimum designed expansion rate at either different depths of running in or different temperatures of steam injection by analyzing pre-stressed insulation tubes of many horizontal wells in the Shengli Oilfield as an example. The comprehensive results showed that the approach to design the optimum expansion rate by this paper could satisfy designed strength requirements of pre-stressed insulation tubes for steam injection wells. The expansion rates of pre-stress insulation tubes at wellhead decreased linearly with the depth of running in during the course of running in,which was much smaller than the expansion rates during steam injection.The force calculation of insulation tube was proposed basing on the tube during the course of steam injection,and the proportional rate was suggested in the design of pre-stress insulation tubes.

Key words: steam injection well, insulation tube, pre-stressed design, proportional expansion rate, mechanics model

摘要：

根据预应力隔热管在制造、下入和注蒸汽等工况下的受力变形特点，建立了基于最佳胀率原理的隔热管内、外管设计计算力学模型，推导出相应工况下隔热管在井口和井底封隔器位置处的最大胀率、最小胀率和比例胀率的计算公式。利用Visual Basic语言编制了相应的计算软件，对胜利油田多口热采井预应力隔热管进行了计算分析，得到了不同下入深度和注汽温度时隔热管最佳胀率设计值。结果表明，最佳胀率设计方法可以满足注蒸汽条件下隔热管强度设计要求；在下入工况下，井口隔热管内外管胀率随下入深度增加而线性减少；在注汽工况下，隔热管的胀率要比下入工况下的增加显著；建议在隔热管胀率设计时要以注汽时隔热管受力为基准，采用比例胀率方法进行设计。

关键词: 注蒸汽井, 隔热管柱, 预应力设计, 比例胀率, 力学模型