Abstract：

   Tahe oilfield, a fractured-vuggy carbonate reservoir in China, has great potential and broad prospects during its oil   development stage. The full development of holes, fractures and vugs in fractured-vuggy carbonate reservoirs in the Tahe oilfield   results in high heterogeneity. The water cone is easily formed during natural energy bottom water development. The displacement   aqueous solution is easily produced along the fractures, causing more remaining oil among wells and a poor result of water   flooding. It is easy to form gas channels during gas injection development. To overcome the issues mentioned above, a smart   nanocard nanofluid with hydrophilicity-lipophilicity was synthesized independently by China University of Petroleum (Beijing) and then utilized to study the ability of profile control and flooding in the laboratory. Smart nanocard is a kind of nano-flake material with sizes of 95 nm in plane and 0.5~1.5 nm in height. The Turbiscan scatterometer was used to evaluate the stability of the smart nanocard nanofluid. The result demonstrated the system was most stable when the concentration of smart nanocard was 50 mg/L. In addition, laboratory experiment results proved that the smart nanocard could intelligently find the oil-water interface and form smart nanocard adsorption layers to change the interface properties. Moreover, the interfacial tension reached 0.6 mN/m and stable emulsions in size of 10 to 50 μm were also formed between simulated oil and water phases when the concentration of the smart nanocard was 50 mg/L. It is also worth mentioning that an oil-wet quartz sheet (contact angle~116°) was transferred into neutral wet (contact angle ~91°). It was also proved that smart nanocard has a mechanism of profile control and flooding according to the results derived from a 2D visualization model and a thin tube model. Besides, it demonstrated that oil displacement efficiency was increased by 9.2 % after smart nanocard flooding in core. Based on the laboratory results, a field test of smart nanocard profile control and flooding technology was initially carried out in the TK779 well groups in Tahe oilfield. Three adjacent wells were significantly affected after 4900 m 3  smart nanocard aqueous solutions were injected (smart nanocard concentration~50 mg/L). The three affected wells increased oil by 2233.9 tons and the average water content decreased from 82% to 25.7 % . Smart nanocard intelligent profile control and flooding technology, as an economical and high efficiency enhanced oil recovery technology, is expected to provide important technical support for the development of later stage fractured-vuggy carbonate reservoirs.  

Key words：smart nanocard; interfacial properties; emulsions; wettability alteration; profile control and flooding; fractured-vuggy carbonate reservoirs

Received： 2019-10-08

Corresponding Authors： houjirui@126.com

Cite this article：LIANG Tuo, HOU Jirui, QU Ming, ZHANG Wei, WU Wenming. 2-D smart nanocard nanofluid laboratory evaluation and field application in fractured-vuggy carbonate reservoirs. Petroleum Science Bulletin, 2020, 03: 402-411.

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