During reservoir engineering analysis, the assessment of the possibility of asphaltene precipitation and corresponding heavy oil recovery with economic losses is carried out before any thermal operation. To investigate this phenomenon, three steam injection experiments using only steam, steam-CO2, and steam- n-C4H10 at 1:1.29 volumetric ratios were carried out in naturally fractured limestone cores saturated with a 12.4° API heavy crude oil. After each experiment, the produced oil's asphaltene content was measured. Further, to determine the asphaltene effect on the fracture apertures and permeability, an improved cubic law (ICL) equation was used to determine the equivalent fracture aperture (EFA) change during the experiments. EFAs were calculated analytically. An initial observation made for only the steam injection experiment was a decline in asphaltene levels present in the producing oil. Asphaltene levels gradually increased as the effects of steam progressed. When CO2 was added to the steam, the asphaltene content of the produced oil increased. Nevertheless, the asphaltene content increased in the produced oil did not change the fracture permeability and EFA considerably. In contrast, when n-C4H10 was injected with steam concurrently, the asphaltene levels gradually increased above the starting value. However, in the further injection period, the asphaltene content in the produced oil was lower than the starting value as the injection progressed. This indicated that a partial upgrading of the asphaltene in the rock matrix caused an improvement in the EFA.