Nano-wetting Reversal Agent And Reversal Mechanism

At present,China's oil demand has increased steadily,while conventional petroleum resources are becoming less and less,and the difficulty of development is increasing,posing a great threat to national energy security.China's tight oil reserves are abundant,making it an important replacement energy source in the petroleum field.Accelerating the development of tight oil has become an inevitable choice.Some studies have shown that the conversion of oil-wet reservoirs to water-wet can effectively improve the recovery of tight oils,while liquids with nanostructures have unique advantages in terms of injectability and improved wettability,and are expected to become the key to tight oil production.In this paper,based on the Jimsar block,we have developed five economical,safe and environmentally friendly nano-wetting reversal agents by adjusting the ratio of main agent,auxiliary agent,polymer and oil phase to particle size test.Based on this,the basic physical properties of the nano-wetting reversal agent were tested,and the basic parameters of the nano-wetting reversal agent for the reservoir were investigated.From the microscopic point of view,the adsorption and microscopic mechanism of nano fluids on rock surface were investigated by total reflection infrared spectroscopy and scanning electron microscopy.From a macroscopic point of view,the nano fluid was tested for interfacial tension with kerosene,contact angle test and core flood test to evaluate the performance of the nano-wetting reversal agent.The results show that the five nano-wetting reversal agents have stable performance,good dilutableness and particle size of 8?25nm.Through the concentration change or formulation change,the particle size and distribution of nano-wetting reversal agent can be controlled,and the nano-run can be controlled.The size of the wet reversal agent;the nano-wetting reversal agent has a wetting reversal function by contact angle,total reflection infrared spectroscopy and scanning electron microscopy,indicating that the nano-wetting reversal agent can be changed within 1-2 hours.The surface properties make it water-wet,and the contact angle of oil droplets increases remarkably.At 0.1% concentration,the interfacial tension is maintained below 2m N/m,which is good for backflow and oil displacement.For the Jimsar block sandstone,nanometer is preferred.Wetting reversal agent 1# has good ability to peel off oil droplets,excellent oil washing effect(efficiency >95%),assisted discharge efficiency(>85%)and starting pressure(half reduction),and nano liquid damage is slightly less than ordinary Helping agent.Based on the above,the mechanism of action of the nano-wetting reversal agent can be summarized based on the experimental results.As the nano fluid passes through the reservoir,the nanoparticles gradually release the surfactant,adsorb on the rock surface,expose the hydrophilic group to the outside,form a micro-nano hydrophilic structure,transform the reservoir into water,and the oil-water interface tension is greatly increased.Reduced and improved oil washing efficiency.