Associative polymer-based fluids for enhanced oil recovery using produced saline water

在加拿大，化学驱目前正被用于提高阿尔伯塔省东部劳埃德明斯特地区和萨斯喀彻温省西部一些中稠油油藏的采收率。根据阿尔伯塔省政府的创新能源技术计划，在未来20年内，化学提高采收率（cEOR）可能会为阿尔伯塔省和萨斯喀彻温省增加8000万立方米的石油储量。仅在美国，就有大约10亿磅聚合物用于cEOR，非常规致密油化学驱的潜力仍未得到充分开发。在cEOR作业中，将聚合物、表面活性剂、碱或其组合等各种化学物质注入井中以提高采收率。然而，不同的油藏作业条件（如pH、温度、盐度、溶解的铁和氧、碱和/或表面活性剂的存在）会影响聚合物的结构和尺寸。具有少量疏水性的水溶性聚合物（称为缔合聚合物）即使在产出水或盐水中也具有提高EOR效率的巨大潜力。尽管近年来在实验室研究中取得了选择性的成功，但一个全面和预测性的知识来回答关键问题仍然是难以捉摸的。该建议的重点是了解常规和致密油油藏中结合聚合物驱的应用机理，并建立预测模型。盐水和智能水由于聚合物线圈的膨胀，可以对缔合聚合物的注入性和输运性能产生积极影响。结合聚合物、表面活性剂和离子相互作用之间的协同效应甚至可以提高碳酸盐岩储层的EOR效率。缔合聚合物驱的机理和矿化度的影响尚不清楚；因此，无法实现最优设计。此外，使用剪切粘度和表观粘度计算的传统毛细管数并不能解释这些结合粘弹性聚合物溶液在不同盐度下显示的不同剩余油采收率。此外，粘弹性聚合物的快速油动员开始发生在毛细数低于临界毛细数。因此，迫切需要通过修改传统的毛细数定义和建立粘弹性缔合聚合物基流体的毛细去饱和曲线来重新建立毛细概念。综上所述，离子溶液、疏水性基团含量和表面活性剂之间的协同效应，除了其他机制外，对粘度、拉伸性能和/或润湿性具有巨大的潜在影响，从而影响提高采收率和压裂效率。拟议的研究计划将解决使用结合聚合物基流体提高采收率的关键技术空白。

In Canada, chemical flooding is currently being applied to increase recovery from a number of medium and heavy oil pools in the Lloydminster region of eastern Alberta and western Saskatchewan. According to the Government of Alberta's Innovative Energy Technologies Program, chemical-enhanced oil recovery (cEOR) could potentially add 80 million m3 of oil to Alberta and Saskatchewan's reserves in the next 20 years. While in the U.S.A. alone approximately 1 billion pounds of polymers were used for cEOR, the potential of chemical flooding in unconventional tight oil remain largely unexplored. In cEOR operations, various chemicals such as polymers, surfactants, alkali or combinations thereof are injected into wells to increase oil recovery. However, different reservoir operating conditions (e.g. pH, temperature, salinity, dissolved iron and oxygen, and presence of alkali and/or surfactant) affect polymer structure and size. Water-soluble polymers with a small amount of hydrophobic character (referred to as Associative Polymers) have huge potential for EOR efficiency even with produced or saline water. Despite selective success in laboratory research in recent years, a comprehensive and predictive knowledge to answer key questions remains elusive. This proposal focuses on understanding mechanisms during associative polymer flooding for applications in conventional and tight oil reservoirs and creating a predictive model. Saline water and smart water can have a positive effect on associative polymer injectivity and transport properties due to polymer coil expansion. Synergistic effects between associative polymer, surfactants, and ionic interactions can lead to increased EOR efficiency even for carbonate reservoirs. The mechanism due to associative polymeric flooding and the salinity effect haven't been clearly distinguished; therefore, optimal design cannot be achieved. Moreover, the conventional capillary number calculated using the shear viscosity and apparent viscosity does not explain the various residual oil recovery shown by these associative viscoelastic polymer solutions at different salinity. Also, rapid oil mobilization for viscoelastic polymers begins to occur at a capillary number lower than the critical capillary number. Therefore, there is a strong need to re-establish capillary concept by modifying the conventional definition of capillary number and developing a capillary desaturation curve for viscoelastic associative polymer--based fluids. In summary, the synergistic effects between ionic solution, hydrophobic group contents and surfactants have huge potential influences viscosity and extensional properties and/or wettability, besides other mechanisms, and thereby EOR and fracking efficiency. The proposed research program will address key technological gaps in EOR using associative polymer based fluids.