Bazyari Armin, Hashemi Abdolnabi, Soulgani Bahram Soltani
Department of Petroleum Engineering, Ahwaz Faculty of Petroleum Engineering, Petroleum University of Technology, Ahwaz, Iran.
Sci Rep. 2025 Jul 2;15(1):22730. doi: 10.1038/s41598-025-05707-5.
Zwitterionic surfactants offer unique physicochemical properties for enhanced oil recovery in carbonate reservoirs; however, their adsorption mechanisms on carbonate reservoir rocks remain incompletely understood. This study presents a comprehensive experimental and theoretical investigation into the adsorption behavior of the zwitterionic surfactant 3-(N, N-Dimethylmyristylammonio) propane sulfonate (ZW4) on calcite surfaces. The effects of key variables including salinity, temperature, pH, and surfactant concentration were systematically examined. Critical micelle concentration was measured under varying salinity and temperature conditions, and a detailed thermodynamic analysis revealed that ZW4 micellization is a spontaneous, entropy-driven process, with enthalpy-entropy compensation ensuring thermodynamic favorability across a wide temperature range. Temperature influenced the CMC non-linearly: it decreased from 10 °C to 30 °C due to reduced hydrophilicity but increased above 30 °C as hydrophobic interactions disrupted micelle formation. The roles of different electrolytes (MgSO₄ and Na₂SO₄) were compared, showing that Mg²⁺ ions significantly reduced the CMC more effectively than Na⁺ ions due to stronger electrostatic double-layer compression and higher ion charge density. At 0.01 M MgSO₄, the CMC decreased from 2000 ppm to 1300 ppm, while Na₂SO₄ at the same concentration reduced it to 1700 ppm. Surface charge modifications of calcite by ZW4 were quantified using zeta potential measurements, which identified a point of zero charge near pH 6.7 and demonstrated increased surface negativity with rising surfactant concentration up to 2500 ppm. This observation is consistent with the pseudo-phase separation model. Higher pH levels inhibited adsorption due to electrostatic repulsion between ZW4's sulfonate group and the negatively charged calcite surface. Increasing salinity enhanced adsorption, transitioning from a "V-shaped" orientation (low packing density) to a more vertical "I-shaped" configuration (high packing density), with MgSO₄ demonstrating a greater effect than Na₂SO₄, attributed to its stronger ability to neutralize surface charge. Adsorption equilibrium data, evaluated using multiple models, identified the Sips model as providing the best fit, highlighting its flexibility in describing complex adsorption phenomena. These findings provide molecular-level insight into zwitterionic surfactant-calcite interactions and underline the importance of thermodynamics, solution chemistry, and mineral surface charge for optimizing EOR surfactant flooding strategies in carbonate reservoirs.
两性离子表面活性剂具有独特的物理化学性质，可提高碳酸盐岩油藏的采收率；然而，它们在碳酸盐岩油藏岩石上的吸附机制仍未完全了解。本研究对两性离子表面活性剂3-(N,N-二甲基肉豆蔻基铵)丙烷磺酸盐(ZW4)在方解石表面的吸附行为进行了全面的实验和理论研究。系统地考察了盐度、温度、pH值和表面活性剂浓度等关键变量的影响。在不同的盐度和温度条件下测量了临界胶束浓度，详细的热力学分析表明，ZW4胶束化是一个自发的、熵驱动的过程，焓-熵补偿确保了在很宽的温度范围内热力学上的有利性。温度对临界胶束浓度的影响是非线性的：由于亲水性降低，从10℃到30℃临界胶束浓度降低，但在30℃以上由于疏水相互作用破坏胶束形成而增加。比较了不同电解质(MgSO₄和Na₂SO₄)的作用，结果表明，由于更强的静电双层压缩和更高的离子电荷密度，Mg²⁺离子比Na⁺离子更有效地降低了临界胶束浓度。在0.01 M MgSO₄时，临界胶束浓度从2000 ppm降至1300 ppm，而相同浓度的Na₂SO₄将其降至1700 ppm。使用zeta电位测量对ZW4对方解石表面电荷的修饰进行了量化，确定了在pH 6.7附近的零电荷点，并表明随着表面活性剂浓度增加到2500 ppm，表面负电荷增加。这一观察结果与假相分离模型一致。较高的pH值由于ZW4的磺酸根基团与带负电荷的方解石表面之间的静电排斥而抑制吸附。盐度增加会增强吸附，从“V形”取向(低堆积密度)转变为更垂直的“I形”构型(高堆积密度)，MgSO₄的影响比Na₂SO₄更大，这归因于其更强的中和表面电荷的能力。使用多种模型评估吸附平衡数据，确定Sips模型拟合效果最佳，突出了其在描述复杂吸附现象方面的灵活性。这些发现为两性离子表面活性剂-方解石相互作用提供了分子水平的见解，并强调了热力学、溶液化学和矿物表面电荷对于优化碳酸盐岩油藏提高采收率表面活性剂驱替策略的重要性。
