The Study On The Influence Law Of Fluid Components In Low Salinity Water Flooding In Carbonate Reservoirs

The Middle East has large geological reserves of carbonate reservoirs and is one of the mainstays of China’s overseas oil and gas interest blocks.In the development of low salinity water flooding,the poor understanding of the interaction law between fluid with rock surface and fluid with fluid within the reservoir has led to poor development results.In this thesis,using carbonate reservoirs as the research object,the effect of reservoir fluid changes on rock surface wettability,oil-water interface stability,residual oil distribution and transport in low salinity water flooding is investigated by the contact angle,oil-water interface stability and microscopic repulsion experiments.The results show that:（1）Different ions affect the rock surface contact angle in different patterns with increasing concentration.The ions in low salinity water affect the wettability by changing the charge and adsorption between the rock and the simulated oil,with Mg²⁺>Ca²⁺>Na⁺and SO₄^2-playing a catalytic role in its presence.Both acid/alkaline components can be adsorbed with the rock,with the adsorption:acidic components>alkaline components.The greater the proportion of acidic components in the crude oil,the more the wettability is biased towards oil wetting.（2）With increasing concentration,different ions have different patterns of influence on the stability of the oil-water interface.Cations in low salinity water affect oil-water interface stability by bridging and changing the charge density at the oil-water interface,where Mg²⁺>Ca²⁺>Na⁺;anion SO₄^2-plays a role in increasing stability and catalysis.When the ion concentration is low,the more acidic components the stronger the oil-water interfacial stability.When the ion concentration is high,the more alkaline components the stronger the oil-water interfacial stability.（3）After water flooding,the remaining oil is island-shaped,angular,continuous,and oil-film-shaped.Low salinity water displaces oil film,horn and column residual oil by changing wettability,emulsifying,impacting and carrying effect.The higher the polar component content,the more distribution of the oil film and angular residuals and the better the mobilisation effect.The lower polar component,the lower distribution of the oil film and angular residuals with the less effective the mobilization.The flow rate increases,the carrying and impact effects are better,and the mobilisation effect is better.