Occurrence Characteristics of Remaining Oil after Steam Huff and Puff in Thin Loose Sandstone Heavy Oil Reservoir

At present, there are few studies on the occurrence characteristics of remaining oil by constructing a “micro-meso-macro” full-scale experimental system. In this paper, the proportion of light and heavy components of target rock samples was tested by a one-dimensional visualization experiment combined with laser confocal microscopy. Then, some rock samples were selected to carry out the NMR T 2 spectrum test and the core thin-section observation experiment. Finally, based on the designed two-dimensional proportional physical model of high temperature and high pressure, the steam stimulation experiment was carried out. The results showed that after two cycles of steam stimulation, the light components in the remaining oil decreased significantly (61.32%→12.36%), and the proportion of heavy components increased. After 3 cycles of steam huff and puff, obvious steam channeling channels could be seen. With the increase of steam temperature (110 °C→180 °C), the utilization degree of light components in the remaining oil increased significantly (42.45%→2.14%). After 5 cycles of steam stimulation, the remaining oil was concentrated in the pores of 0–1 μm. The remaining oil bands and steam channeling channels formed in the thin sections of the core can be seen. The steam-swept area of the vertical well was centered on the huff and puff well to form a breakthrough into the stable pressure well, while the steam-swept area of the horizontal well was centered on the huff and puff well. After 7 rounds of steam stimulation, the remaining oil was distributed in the nonmainstream line area.