First, the extracellular poly γ-(glutamic acid) (PGA) was synthesized by bacillus licheniformis LMG 7559. Then, the applicability of this biopolymer in the microbial enhanced oil recovery (MEOR) was evaluated. The impact of sulfate ions, as strong potential determining ions (PDI's) toward carbonate surfaces, on the stability and performance of PGA flooding, was investigated. The stability of the PGA solution was reduced by increasing the biopolymer content and adding salts. The contact angle measurement showed that sulfate ions played an important role in altering of wetting state to a water-wet condition (less oil-wet). After the treatment of glass and carbonate rock plates in the PGA solution (0.25% w/v), the contact angles were changed about 18 and 44 units, respectively. Also, the PGA solution with a two-fold concentration of typical sulfate ions content (SBP#2 S) changed the contact angle about 47-fold and 92-fold at the glass and rock surfaces, respectively. It was concluded that the SBP#2 S decreased the surface charge of carbonate rock to the value of −6.5 mV compared to the sulfate-free sea brine-PGA solution (SBP#0 S) with the value of −2.3 mV. Furthermore, the adsorption of PGA onto the carbonate particles and the fluids viscosity as well as the interfacial tension (IFT) between PGA solution and crude heavy oil were examined. We observed that as the PGA content increased to 0.5% w/v, PGA adsorption on the carbonate rock surface increased to 21.1 mg/g. The Freundlich isotherm model was more acceptable for the experimental results than the Langmuir model. Also, the results of viscosity measurement showed that the viscosity of PGA solutions decreased in the presence of the salts. Stable fluids were injected in a quarter five-spot heterogeneous glass micro-model. The PGA solution with the content of 0.5% (w/v) recovered 31.45% of oil in place and the SBP#2 S produced 27.82% of oil in place compared to the SBP#0 S solution (19.1%).

首先，通过地衣芽孢杆菌合成胞外聚γ-（谷氨酸）（PGA）LMG7559。然后，评估了这种生物聚合物在微生物提高采油率（MEOR）中的适用性。研究了硫酸根离子作为强势决定性离子（PDI）朝向碳酸盐表面的影响对PGA驱油的稳定性和性能的影响。通过增加生物聚合物含量和添加盐，PGA溶液的稳定性降低。接触角测量表明，硫酸根离子在将润湿状态改变为水润湿状态（少油润湿）方面起着重要作用。在PGA溶液（0.25％w / v）中处理玻璃板和碳酸盐岩板之后，接触角分别改变约18和44个单位。也，具有两倍典型硫酸根离子浓度（SBP＃2 S）浓度的PGA溶液在玻璃和岩石表面的接触角分别改变了约47倍和92倍。结论是，与无硫酸盐海盐水-PGA溶液（SBP＃0 S）的-2.3 mV值相比，SBP＃2 S将碳酸盐岩的表面电荷降低到-6.5 mV的值。此外，还检查了PGA在碳酸盐颗粒上的吸附和流体粘度以及PGA溶液与原油重油之间的界面张力（IFT）。我们观察到，随着PGA含量增加到0.5％w / v，PGA在碳酸盐岩石表面的吸附增加到21.1 mg / g。Freundlich等温模型比Langmuir模型更能接受实验结果。也，粘度测量的结果表明，在盐的存在下，PGA溶液的粘度降低。在四分之一的五点异质玻璃微模型中注入稳定的流体。与SBP＃0 S溶液（19.1％）相比，含量为0.5％（w / v）的PGA溶液在原位回收了31.45％的油，SBP＃2 S在原位回收了27.82％的油。