Abstract:

Heating formation to reduce crude oil viscosity is one of the main mechanisms of cyclic steam stimulation (CSS). A dynamic heat transfer model considering both thermal convection and thermal conduction was established. Coupling temperature and pressure fields, this model was used to determine formation pressure, formation temperature, and fluid convection velocity, so that the dynamic variation of formation heat was analyzed. The research results show that, in the steam injection stage, given the same cyclic steam injection volume, higher heating rates and net heat are achieved when the injection duration is 6.0-10.0 days. In the soaking stage, when the pressure stops rising, thermal convection weakens rapidly, and formation heating rate significantly decreases, with an 88.3% drop in heating rate after 4.0 days of soaking, allowing for well production. In the production stage, thermal conduction becomes the dominant mechanism, and the formation heat increases slowly and steadily. After one cycle of CSS, 57.7% of the incremental heat is recovered with the produced fluid, while 42.3% remains in the formation. This study provides a deeper understanding of the formation heat variation during CSS, which supports the optimization of injection-production parameters and the analysis of steam heat flow.

Key words: CSS, formation heat, crude oil viscosity, thermal convection, thermal conduction, temperature field, heating rate