- freely available
Processes 2020, 8(1), 93; https://doi.org/10.3390/pr8010093
2. Experimental Section
2.1. Materials and Apparatus
- Homogeneous cores. The dimensions are 25 mm in diameter and 500 mm in length. Gas permeability is 2500 mD. Water permeability is 810 mD.
- Three-layered heterogeneous cores. The dimensions are 45 mm in width, 45 mm in height, and 300 mm in length. The permeabilities of three layers from top to bottom are 5000/2000/500 mD, respectively.
- Electrode-bearing core. This type of core is used to measure the remaining oil distribution. A schematic and a picture of the core sample setup are shown in Figure 1. Copper electrodes were installed along the core samples, at an interval of 3.3 cm.
2.2. Experimental Procedures
2.2.1. Macroscopic Oil Displacement Experiment
- Measure the gas permeability.
- Vacuum saturate the core sample with brine in Table 1 and calculate the porosity according to the weight difference.
- Measure the water permeability by injecting brine at different flow rates.
- Inject oil at successive flow rates of 0.1, 0.2, 0.5, and 1.0 mL/min, to displace water until no more water is produced. Age the core at 65 °C for 72 h.
- Polymer solution (0.3 PV) is injected at 1.0 mL/min, at different water saturations.
- A post-waterflooding is carried out at a flow rate of 1.0 mL/min till the instantaneous water cut reaches 95%. Throughout the displacement test, a 10 mL glass tube is used to collect the effluent every 5 min.
2.2.2. Microscopic Oil Displacement Experiment
- Setup the microfluidic system and check its leakage. Then fill the micromodel with brine.
- Inject oil at a rate of 0.001 mL/min.
- Then inject brine at 0.001 mL/min and the whole process is recorded by using a computer and a camera.
- Inject polymer solution at 0.001 mL/min for 0.3 PV.
- A post-waterflooding is conducted at 0.001 mL/min until water cut reaches 95%.
- Data processing: the oil saturation change in each pore of the micromodel is calculated according to the pixel value which is processed by Photoshop and Image J.
3. Results and Discussion
3.1. Polymer Injection Timing Analysis by Macroscopic Oil Displacement Tests
3.2. Polymer Injection Timing Analysis by Microscopic Oil Displacement Tests
3.2.1. Comparison of Waterflooding with Polymer Flooding at Secondary Mode before Water Breakthrough
3.2.2. Microscopic Displacement at Different Polymer Injection Timing
3.3. Polymer Injection Timing Determination by Buckley–Leverett Method
3.4. Effect of Polymer Injection Timing on Residual Oil Distribution
Conflicts of Interest
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|Ion Types||Na+ and K+||Ca2+||Mg2+||CO32−||HCO3−||SO42−||Cl−||TDS|
|Water Volume Injected Before Polymer Flooding|
|Homogeneous core||0.07 PV||0.14 PV||0.20 PV||0.27 PV||0.36 PV|
|Heterogeneous core||0.03 PV||0.07 PV||0.10 PV||0.13 PV||0.20 PV|
|Polymer Injection Timing||Oil Recovery of Waterflooding||Oil Recovery of Polymer Flooding||Final Oil Recovery|
|Sw = 15.42%||15.42%||37.92%||69.17%|
|Sw = 42.79%||42.79%||47.15%||60.12%|
|Sw = 38.83%||38.83%||52.27%||86.33%|
|Time (min)||Water Front Position (cm)||Injection PV|
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