防止热采井套管热破坏的预压固井技术

热力采油是开采稠油的最广泛、效益较高的方法。实践表明:注蒸汽稠油井如果用常规方法固井,那么在通常的注汽温度下,套管都因热应力而产生屈服变形。目前现场常用的防止套管热破坏方法不能从根本上解决问题。该文提出了防止热采井套管热破坏的预压固井技术,即在注水泥结束但没有凝固时,向油层套管施加内压强,使套管膨胀;水泥在套管膨胀的条件下凝固。计算表明:采用预压固井技术后,热采井在整个生产周期内,套管不但不屈服,而且还有较大的安全系数。此项技术可能成为延长热采井套管使用寿命的重要手段。

CASING CEMENTING WITH INTERNAL PREPRESSURIZATION FOR THERMAL RECOVERY WELLS

The thermal recovery is a very common and effective method for producing heavy oil. The casing failure is a very serious problem in thermal recovery wells. In steam injection process, casing is heated by steam. The change of casing temperature produces thermal stresses in the casing. The casing deforms when stresses exceed the yield point of its material. If using conventional cementing technology for thermal recovery wells, the casing deforms due to thermal stresses in steam injection process. Technologies conventionally used to protect the casing from failure for thermal recovery wells are inefficacy theoretically. The casing cementing with internal prepressurization for thermal recovery wells refers to exert inner pressure on payzone production casing and make payzone production casing expand in the cement solidifying period. The calculations show that the casing with internal prepressurization technique performs greater safety coefficient during the whole production cycle and no plastic deformation. This technique will be an important method to prolong the casing life of the thermal recovery well.