What are the effects of polymers on dehydration?
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Polymer flooding has improved the recovery rate of crude oil, but it also has an impact on surface water separation. Different oil fields employ various processes and methods for treating the fluids produced as a result of polymer flooding. However, what exactly is the impact of polymers on surface water separation, and which process is the most suitable? We welcome discussions on this topic.
Mainly, there is a high amount of oil in the water, making it difficult to remove. The School of Chemistry and Chemical Engineering at China University of Petroleum (Huadong) carried out sub-component separation of the oil, water, and other components in the produced fluid from isolated oil fields using polymer injection for oil recovery, studied the impact of each sub-component on emulsification and demulsification, and resolved such issues. The oil content in water is significantly reduced, and the cost is not high. This project won first prize from Shengli Oilfield and second prize from Sinopec.
It is generally believed that it affects emulsification and demulsification, but how exactly does it do so? Could you explain it from a mechanistic perspective? Are there any other effects as well, such as the charge carried, surface tension, etc.?
Polyacrylamide is injected into the ground, where it degrades and hydrolyzes in the formation; with a molecular weight of 1–4 million, it acts as an excellent dispersant that significantly improves the stability of oil in water.
(1) Effect of polyacrylamide on wastewater viscosity: The viscosity of wastewater increases as the concentration of the polymer (HPAM) rises, affecting the oil-water separation efficiency of the separator. (2) Effect of polymers on interfacial elasticity: When two oil droplets come close to each other, a water film forms on the surface of the oil droplets. For two drops to merge into one, the water film must be broken. Therefore, the strength of the water film determines the ease of oil droplet coalescence. The interfacial elasticity increases as the polymer concentration rises, indicating that the polymer makes it more difficult for oil droplets to coalesce. (3) Stability of polymer-containing solutions The negatively charged polyacrylamide molecules increase the electronegativity of oil droplets and suspended solids, enhancing their stability in water. Tests were conducted on the stability of oil-in-water emulsions, and it was found that the amount of water released decreased as the polymer concentration increased, indicating that stability increases with rising polymer concentration. (4) The particle size of oil droplets in the injection polymerization production water is small; 88.1% of the total number of oil droplets have a particle size distribution ranging from 2 to 10 μm. The solid suspended particles in water are relatively large in size and have a wide distribution range, mainly falling between 2.6 μm and 15.4 μm. Among them, particles smaller than 5 μm account for 22.6% of the total volume. As a result, the oil droplets in the water produced by injection polymerization are small in size while the suspended particles are large, which makes oil-water separation more difficult.