Study On The Influence Of Ion Kinds And Concentrations To Wettability Of TZ4 Sandstone Reservoir

Low salinity water flooding possesses many features,such as easy to operate,low investments,abundant water resources,low environmental pollution,etc,therefore it has larger development space in the tertiary oil recovery.After many years of research,there are a lot of controversies in studying the mechanisms of low salinity water flooding to improve oil recovery.This paper studies the influence of low salinity water to the reservoir wettability through experiments.This paper adopts the Zeta potentiometer,interfacial tensiometer,contact Angle measurement instrument,imbibition experiments,water flooding experiments,scanning electron microscopy and X-ray diffraction spectroscopy experiments,studies the influence of different ion and different salinity solutions on the surface force and oil recovery,and exploring the impact of low salinity water flooding through the micro-experiments,finally perfects the mechanisms of low salinity water flooding to improve oil recovery.Results show that 0.05mol/L NaCl was the optimal ion component to improve oil recovery and pH = 3 was the isoelectric point of the Tarim oil reservoir.There are two mechanisms of low salinity water flooding to improve oil recovery:?1?Reducing the salinity of brine will expend the diffused electric doublet layer of rocky surface and oil-water interface,increasing the absolute value of Zeta potential,enlarging the electrostatic repulsion between rocky surface and oil-water interface;?2?Na+ replace Ca²⁺ which takes the bridging role between crude oil and rock.Both mechanisms can enhance the rock surface hydrophilicity.Eventually improve the oil recovery.