Review on mechanisms of petrophysical properties variation during thermal fluids injection into heavy oil reservoirs

Thermal fluids-induced variation petrophysical properties are non-negligible for heavy oil well production performance during thermal recovery, which has been studied and discussed for more than half a century, and many mechanisms and factors have been found. However, these achievements and findings on these trigger mechanisms and factors are too complicated and scattered, and they have not been collected and unified in the academic field so far. In addition, due to the complex relationship between these mechanisms and factors, many previous works have failed to completely achieve research goals. The purpose of this review is to critically discuss the shortages of previous works based on a systematic summary. Furthermore, some specific suggestions and novel perspectives are proposed to provide a feasible direction to achieve better research results. We have reviewed literatures on thermal fluids-induced petrophysical properties changes of reservoir rock nearly the last 50 years, and 8 mechanisms and 37 factors were detailly described and analyzed. Previous works are usually discussed by dividing into (1) single mechanism/factor research and (2) multi-mechanisms/factors research. The shortages of the two types studies respectively are (1) the difficulty in eliminating influence of other interference mechanisms and factors, and (2) the failure to consider all potential mechanisms and factors. Therefore, (1) further research should focus on the triggering limits of various mechanisms and factors, and (2) use larger-scale experiments to simulate real conditions. These two potential methods may overcome the abovementioned shortages of previous works. Certainly, we believe that correct consideration of various mechanisms and factors is the key and basis for future studies.