Synthesis and Performance Evaluation of Polyhydroxy Benzene Sulfonate Oil Displacement Agent Based on Enhanced Interfacial Wettability Control

Controlling the wettability of the oil-rock interface is an important way for highly efficient oilfield development. For existing anionic surfactants, their capability of changing the wettability of the rock surface is limited. Therefore, developing novel oil displacement agent with enhanced interfacial wettability control capability is of great significance. In this work, an interfacial wettability controlling oil displacement agent, sodium dimethyloldodecyl benzene sulfonate (SDDBS), was synthesized and the structure was characterized by Fourier transform infrared (FT-IR) and H-1-nuclear magnetic resonance (H-1 NMR). The critical micelle concentration (cmc) of SDDBS was measured by spinning drop method and was determined as 0.02% (w). The adsorption behavior of SDDBS on oil-wet rock surface, the interfacial tension reduction property, wettability controlling property, oil film peeling performance and the oil displacement performance were evaluated. Based on the atomic force microscopy (AFM) images, SDDBS could adsorb uniformly on the surface of oil-wet rocks. The oil/water interfacial tension could be reduced to 2.54 mN/m under cmc. After immersing the oil-wet glass sheet in 0.02% (w) SDDBS solution for 48 h, the contact angle of the glass sheet towards water drop in air reduced from 100.2 degrees to 24.5 degrees, while the contact angle towards oil drop underwater increased from 19.2 degrees to 153.9 degrees, proving that SDDBS could regulate the wettability of the oil-wet/hydrophobic rock surface to strong hydrophilic/underwater oleophobic state. The oil film peeling performance of SDDBS was evaluated by calculating the remaining oil film area by graphical analysis software. When soaked in 0.02% (w) SDDBS solution at 60 degrees C, the area of oil film could be reduced by 89% within 24 h. The oil film reduction rate could still reach 81% in simulated formation water, indicating good reservoir adaptability. Laboratory simulation core displacement experiments were conducted at 60 degrees C and the results showed that the oil recovery rate was increased by 10.53%. In this work, a novel polyhydroxy benzene sulfonate surfactant was synthesized by one-step method. By introducing hydrogen bond to enhance the interfacial wetting control ability of surfactant, the oil film could be peeled off efficiently, exhibiting strong practical application potential.

Automated summary

A novel oil displacement agent, SDDBS, was synthesized and characterized. The adsorption behavior, interfacial tension reduction, wettability control, oil film peeling, and oil displacement performance were evaluated. The results showed that SDDBS could uniformly adsorb on the rock surface and effectively control the wettability of the oil-rock interface.