Experimental and numerical investigation of coupled radial electroosmotic flow and electric field using pi electrokinetic up-scaled reservoir model

The application of electrokinetic phenomena in the petroleum and environmental engineering has been developing since the last few decades with promising results in both laboratory studies and field pilots. Electrokinetic Enhanced Oil Recovery (EKEOR) is gaining increased popularity due to a number of reservoir-related advantages such as reduced water-cut, reduced HSE concerns, increased reservoir permeability and no depth of limitation. All previous studies have used one-dimensional (1-D) electrode configuration to apply electric field during EK treatment and have consistently proved that recovery enhances 2 to 3 fold owing to electroosmotic mobilization or enhanced viscous drag forces while increasing reservoir permeability. However, there is lack of experimental research conducted on the feasibility of applying multiple electrode configurations in sandstone and carbonate reservoirs to enhance this process. This study closely examines radial electroosmotic flow with the help of an up-scaled laboratory reservoir model designed at the Petroleum Institute to compare the performance of various two-dimensional (2-D) electrode configurations in enhancing electroosmotic flow rate and reservoir permeability while targeting minimum power consumption, induced current density and electrode life.;Radial electroosmotic flow is achieved by superimposing brine injection and electric field application in radial directions towards the central cathode / production well and multiple anodes / injection wells located at the periphery of the reservoir model. The porous medium consists of sandstone (250mum or 500mum) or carbonate (250mum) lithology. The medium is saturated with either 4 % or 0.4 % NH4Cl (in order to simulate 4,000 ppm -- 40,000ppm salinity condition) in the first stage. In subsequent stages, electric field is applied using a constant potential gradient of 0.5 V/cm to 1V/cm. During the experiments, the average and cumulative electroosmotic flow rates, liquid permeability, voltage distribution and pH were observed and compared. Numerical simulation is also carried out to compute pressure and electric field distribution for the different electrode configurations.;The experimental results demonstrate that for a sandstone reservoir with 250mum grain size, the flow rate varies with different electrode configurations according to salinity conditions and applied voltage gradient. The radial configurations show a 15-50% increase in permeability enhancement and a 15-88% increase in electroosmotic flowrates compared to 1-D linear configurations.The best results for permeability enhancement and electroosmotic flowrates with 2-4% reduced power consumption and induced current density is obtained with the 6:1 electrode (six anode-one cathode) configuration. The 4:1 electrode and 3:1 electrode patterns also show significant permeability enhancement and electroosmotic flow rates although their electroosmotic efficiencies are lower than the 6:1 configuration. Numerical simulation results demonstrating the distribution of electric field, potential, pressure and the velocity vector field show close correlation with experimental results obtained with the reservoir model.