Study On NPS-1 Petroleum Sulfonate And Its Applied Properties

Complex Chemical flooding is an important enhanced oil recovery (EOR) technology. Alkaline, surfactant and polymer are combined effectively in this method, thus oil-displacement efficiency is increased greatly. Petroleum sulfonate is a kind of anionic surfactant synthesized by raw material of oleum distillates. As oil displacement agent it possesses high interfacial activity, compatibility with reservoir fluids and good water solubility. Thus much attention has been paid to it. The composition of raw material is complex, thus the composition and structure of petroleum sulfonate is complex. Furthermore, the composition and property among petroleum sulfonate products is different. The surfactants for EOR which possess low interfacial tension(IFT) and low adsorptive loss can increase oil-displacement efficiency, thus researching petroleum sulfonate with high interfacial activity and low adsorptive loss are of great significance.In this paper, a kind of petroleum sulfonate (NPS-1) was synthesized in single-tube film sulfonation reactor. The chemical structure and composition of products is characterized. The colloid and interface chemistry properties were studied such as surface tension, oil-water interfacial activity and adsorption property on solid medium. The oil-displacement efficiency was also investigated in core-flooding experiments. Furthermore, NPS-1 is separated into fractions with different average relative molecular mass by means of solvent extraction. The molecular structure and interfacial chemistry property of fractions are investigated. And the effect mechanism of the structure of petroleum sulfonate on the interface chemistry properties and the applied performance is studied, which providing the theoretical guidance for synthesizing petroleum sulfonate with high efficiency and low cost.The results show that NPS-1 is synthesized in film sulfonation reactor by the raw material of Suizhong36-1 No.2 or No.3 vacuum cut gas oil and SO₃ sulfonation agent. The yield and surfacial activity of petroleum sulfonate synthesized under optimized sulfonation conditions is high. NPS-1 possesses appropriate average relative molecular mass and its average relative molecular mass distributes within broad range. Thus it is fit for enhanced oil recovery as oil-displacement surfactant.NPS-1 is separated into four fractions with different average relative molecular mass. The molecular structure, interface chemistry property and oil-displacement performance of the fractions are different significantly. Synergism of components is different, which is related to the molecular structure of components, mixture ratio and oil phase. The IFT between NPS-1 fractions solution and kerosene oil possesses correlation withζpotential.Turning point of the IFT curves of NPS-1 solution-oil phase system is at the concentration 0.0025g/mL, which is the critical micellar concentration (CMC). The addition of NaCl, NaOH and Na2CO3 can decrease the IFT. Different alcohol have different effect on the IFT of petroleum sulfonate-oil phase system. The synergism between petroleum sulfonate and other surfactants exhibits selectivity.ζpotential absolute value of NPS-1 solution- kerosene oil system increases and then declines with the increase of NPS-1 concentration. NaCl and Na2SO4 can decreaseζpotential absolute value of the system.The static adsorption of NPS-1 on Gudao reservoir sand reaches maximum at the CMC. The static adsorption decline continueously with the increase of pH value. The effect of different electrolytes on the adsorption of NPS-1 is different. HPAM can increase the static adsorption of NPS-1 at low concentration.The optimum oil-displacement agent prescription is selected for crude oil of Well15-403 and reservoir water of Shengli Oil Field, which is 0.0010g/mLNPS-1+ 0.0040g/mLNinol. This oil-displacement agent solutions can increase the water-flooding oil recovery from 38.1% to 65.9%, thus it possesses good applying prospect.