科研之友
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摘要
Carbonate reservoirs hold significant reserves of heavy crude oil that can be recovered by nonthermal processes. Chemical-enhanced oil recovery from oil-wet carbonate reservoirs has focused on the use of surfactants to change wettability and enhance imbibition into the matrix; however, the fractured nature of carbonate formations makes oil recovery a challenging process. Recently, developments in foam/polymer-enhanced foam (PEF) injection for heavy oil recovery application have come about, but the process of PEF for carbonate reservoirs is still not fully understood. This paper introduced a new approach to accessing the heavy oil from fractured carbonate reservoirs. foam/PEF was used to decrease oil saturation after surfactant flooding. Three types of surfactants (nonionic, anionic, and cationic) were used for both surfactant and foam flooding. A specially designed fractured micromodel representing a porous media system was used to visualize pore-scale phenomena. In addition, the static performances of foam/PEF were analyzed in the presence of heavy crude oil. The results showed that in both static and dynamic studies, the PEF had higher stability than the foam. Nonionic surfactant generated the least stable foam in the presence of crude oil. Surfactant flooding slightly increased the oil recovery from matrix after water injection. This was more evident in the case of cationic surfactant with highest imbibition rate. Observation through this study proved that stable foam/PEF bubbles can significantly push the injected fluid toward untouched parts of the porous media and increased the oil recovery. Due to the liquid viscosity enhancement and bubble stability improvement, the effectiveness of PEF in heavy oil sweep efficiency was much higher than that of conventional foams. PEF bubbles generated an additional force to divert surfactant/polymer into the matrix.
- 出版日期2016-7
