Assessing the Environomic Feasibility of Electrokinetic Low-Concentration Acid IOR in Abu Dhabi Carbonate Reservoirs

Abstract

Abstract EOR (Enhanced Oil Recovery) and IOR (Improved Oil Recovery) have been at the forefront of oil and gas R&D for the past 4 decades as currently, more than 1500 field pilots have contributed to 3.5% of daily EOR/IOR production which is expected to increase upto 10% in 2050. However, the petroleum industry is faced with a number of challenges when considering the reservoir such as low sweep efficiency, formation damage and implementing costly techniques to enhance and improve the oil recovery. Electrokinetic Low-concentration acid IOR (EK LCA- IOR) is one of the emerging EOR/IOR technologies, applied by integrating Electrokinetics with matrix acid stimulation, which is gaining increased popularity as it increases reservoir permeability, reduces HSE concerns of acidizing and increases targeting of the unswept oil. This research demonstrates the effectiveness of the EK LCA- IOR process and assesses its environomic feasibility in Abu Dhabi carbonate reservoirs. Laboratory core-flood experiments were conducted on Abu Dhabi carbonate rock samples, saturated with medium crude oil in a specially designed EK core-flood setup at reservoir conditions. After the waterflooding stage, LCA- IOR flooding complimented by electrokinetics is performed to implement a number of mechanisms using varying voltage gradients and acid concentrations upto 1.2% HCl. Moreover, the permeability enhancement, ultimate oil recovery and capillary number change were analyzed to quantify the success of the process. The EK LCA-IOR process was also compared with other Electrokinetic recovery processes such as Electrokinetic-EOR, EK-Surfactant EOR and EK-Nano EOR to assess the environomic profitability of each process. Several correlations related to acid concentration, displacement efficiency, permeability enhancement and environomic unitless index have shown, that the application of waterflooding yields an average oil recovery of 58%. An additional 17–28% recovery was enhanced by the application of EK LCA-IOR, recording a maximum oil displacement of 88%. In addition, the reservoir's permeability was enhanced by 53% on average across the tested core-plugs where stimulation takes place by effective EK transport of the injected and in-situ acid from the anode towards the target producer (cathode). EK LCA-IOR also improves the capillary number by 400% in Water-wet core-plugs and 1600% in Oil-wet core-plugs, mainly due to a decrease in interfacial tension. This could be promising for water-swept and oil-wet reservoirs as this technique can significantly improve economic sustainability giving the highest unitless index, by reducing CAPEX/OPEX 10 times more as compared to other EK-EOR approaches. The optimized acid concentration (~1.2%) and voltage gradient (~1V/cm) can provide formation stimulation upto 53% and oil recovery upto 88%, while reducing the acid/water requirement by 70% and power consumption by 20%. This study takes one step forward towards the development of EK LCA-IOR method feasible for Abu Dhabi oil fields in order to make smart waterfloods applicable for complex fractured reservoirs.