热采井套损机理及套管强度优化设计

我国稠油资源丰富，然而稠油热采井套管损坏现象普遍存在，且有越来越严重的趋势，提高热采井套管寿命是稠油开采过程中迫切需要解决的问题。分析了热采井套管损坏主要原因，认为高温引起的强度变化、油层出砂亏空、固井质量差、隔热措施不利及套管本身材质问题都有可能引起热采井套管损坏。采用有限元分析软件ANSYS计算了不同隔热措施、不同注汽温度、不同注汽压力、不同套管材料及壁厚条件下套管应力分布规律。计算结果表明，为减少稠油热采井套管损坏，采用隔热措施较好的油管可以明显降低套管上的等效应力，同时在套管柱设计过程中应优选低弹性模量、厚壁套管。提出了VonMises等效应力对比高温屈服强度的校核新方法，为稠油热采井套管强度设计提供依据。

Casing failure mechanism of thermal production wells and casing strength optimization design

There are a number of heavy oil in our country, and the casing failure generally exists in heavy oil thermal recovery production, which becomes more and more serious. Improving the casing life of thermal recovery well has become a problem to be urgently solved in heavy reservoir thermal recovery production. The main reasons of casing failure in thermal recovery wells were analyzed. Strength change with high temperature, sanding in reser- voir, poor cementing, unfavorable heat insulation and bad material for casing could all cause casing failure. Casing stress law was calculated by ANSYS finite element analysis software under different insulation, different steam in- jection temperatures, different steam injection pressures, different casing material and thickness. The results showed that in order to reduce casing failure in heavy oil thermal production, adopting oil tube with good heat insu- lation can reduce equivalent stress of casing effectively, and the casing should be optimized with low elastic modu- lus, thick-walled casing to reduce casing failure in heavy oil thermal recovery wells. A new checking method adop- ting Von Mises equivalent stress comparing with high temperature yield strength of casing was proposed, which pro- vides the basis for casing strength design in heavy oil thermal recovery wells.