The problems of low drilling efficiency and low core recovery due to borehole collapse were solved with pulling in casing while drilling through using combined BHA with casing.
This technology keeps the casing in an elastic state in the whole thermal recovery process without plastic deformation taking place, and thus resolves the problem of thermal casing failure.
该技术可使套管在整个开采过程中一直处于弹性状态，不发生塑性变形，从而解决了套管热破坏问题。
3
Most of the models calculating casing thermal stress in thermal recovery well belong in a monoaxial stress analysis because of neglecting the effect of formation.