After the"horizontal well+volume fracturing"technology transformation and development has been performed in tight oil reservoirs,there appear the problems that cross flow happens between wells'fluid and the recovery rate of tight oil becomes low.In order to solve these problems,a high foaming and strong permeable nano oil displacement agent is developed.The self-developed gemini surfactants including BD-2,CHSB and LAB are used as main agents of nano oil displacement agent,the formula of nano oil displacement agent is obtained through ternary phase diagram method as follows:25%BD-2+10%LAB+4.5%CHSB+5%oil-soluble synergist+15.5%small molecule alcohol.The interfacial properties,wetting adjustment performance,imbibition performance,foaming performance,temperature resistance,salt resistance,compatibilization performance and static oil washing performance of the agent are evaluated.Meanwhile,the application of the nano oil displacement agent to tight oil in core is studied.The results show that at 2 000 mg·L-1,the interfacial tension between YYC-2 nano oil displacement agent and Mahu crude oil can reach 6.318×10-3 mN·m-1,and the contact angle can be reduced to 20.36°.The degree of imbibition recovery reaches 21.37%.It can reach the ultra-low interface level at 90℃,10×104 mg·L-1 NaCl and 5×103 mg·L-1 CaCl2 salinity.The maximum compatibilized particle size can reach 593.6 nm.The maximum static oil washing efficiency can reach about 80%.The conversion coefficient between high-pressure mercury injection curve and nuclear magnetic resonance curve is 791 nm·ms-1,and the minimum pore diameter that can start the core is 20.030 4 nm.
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