Investigation of Electrokinetic Low-concentration acid IOR (EK LCA-IOR) for Abu Dhabi carbonate reservoirs

  • Arsalan Arshad Ansari

    Student thesis: Master's Thesis


    Electrokinetic Low-concentration acid IOR (EK LCA-IOR) is one of the emerging IOR technologies which involves the application of the Low-concentration acidizing integrated with electrokinetic enhanced oil recovery (EK-EOR) conducted on Abu Dhabi carbonate core-plugs. This approach is gaining increased popularity due to a number of economic and reservoir-related advantages such as reduction in fluid viscosity, reduced water-cut, increased reservoir permeability, reduced HSE concerns, increased targeting of the unswept oil and enhanced depth of penetration. This research work demonstrates the impact of Electrokinetics (EK) on matrix acid stimulation in carbonate reservoirs with varying acid concentrations and voltage gradients. Core flood tests were performed by saturating core plugs retrieved from Abu Dhabi producing oilfields with light and medium crude oil in a specially designed EK coreflood setup. After the waterflooding stage, EK was applied using acids of varying voltage gradient and varying concentrations from 0.125 to 1.2% HCl injected at the anode at 0.25 ml/min (consistent with an average reservoir flow rate of 1 ft/day) and transported by EK to the target producer (cathode). Experiments were also repeated with conventional LCA-IOR with and without the application of EK. The reservoir rock permeability and ultimate oil recovery were measured before and after each experiment to quantify the success of the process. This was compared with sequential and simultaneous application of EK LCA-IOR in water-wet and oil-wet rocks at ambient and reservoir conditions. The EK LCA-IOR process was compared with other Electrokinetic recovery processes such as Electrokinetic-EOR (EK-EOR), EK-Surfactant EOR and EK-Nano EOR to compare the environomic profitability of each project. Moreover, the wettability and capillary number change for the EK LCA-IOR process was also modelled in order to develop an optimum process that allows us to shift from a conventional to simultaneous EK LCA-IOR process. Several correlations related to acid concentration, displacement efficiency, permeability enhancement, current density and power consumption are presented here for both water-wet and aged oil-wet core-plugs at ambient and reservoir conditions. The experimental results have shown that the application of waterflooding on the carbonate cores yields an average oil recovery of 60%. An additional 17-28% oil recovery was enhanced by the application of EK-assisted low-concentration acid IOR (EK LCA-IOR) recording a maximum oil displacement of 88% at reservoir conditions which is higher than sequential EK LCA-IOR (77%) and Conventional LCA-IOR (66%). In addition, Simultaneous EK LCA-IOR was shown to enhance the reservoir's permeability by 53% on average across the tested core-plugs at reservoir conditions which is higher than 32% (Sequential EK LCA-IOR) and 24% (Conventional LCA-IOR). This could be promising for water-swept and oil-wet reservoirs due to in-situ stimulation by co-generation of the free acid at the anode as well as high performance EK transport of the injected acid. Furthermore, this technique can be engineered to be a sustainable approach in the presence of EK as the concentration and voltage gradient can be optimized to reduce the amount of acid injected and power consumption by 20-41%, further improving economic feasibility. A model was developed to optimize the capillary number change impacted by EK and LCA-IOR with maximum displacement efficiency and maximum permeability enhancement to optimize the concentration and voltage gradient feasible in tight carbonate reservoirs while reducing the power consumption and amount of acid injected. EK LCA-IOR causes an increase in the capillary number (Nc) by 400% to 600 % in Water-wet core plugs and 1000% to 2200% in Oil-wet core plugs due to an increase in the fluid velocity and viscosity and dominated mainly by the decrease in interfacial tension caused by the modified EK LCA-IOR process, that leads to an increase in recovery factor and thus altering wettability. Finally, EK LCA-IOR also allows us to save on the CAPEX and OPEX by optimizing the process and maintaining a low current density with reduced power consumption while reducing the fluid (acid/water) requirement upto 10 times as compared to conventional EOR/IOR. This study takes one step forward towards the development of a low-concentration acid IOR method feasible for Abu Dhabi oil fields.
    Date of Award2014
    Original languageAmerican English
    SupervisorMohamed Haroun (Supervisor)


    • Applied sciences
    • Nanotechnology
    • Petroleum engineering
    • 0765:Petroleum engineering
    • 0652:Nanotechnology

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