Distribution Characteristics of Micro Remaining Oil of Class III Reservoirs after Fracture Flooding in Daqing Oilfield
Abstract
:1. Introduction
2. Fracture-Flooding Technology
3. Study on the Distribution Characteristics of the Microscopic Remaining Oil in Fracture-Flooding
3.1. Design of Fracture-Flooding Experiment Scheme
3.1.1. Experimental Materials
3.1.2. Experimental Equipment
3.1.3. Experimental Design Scheme
3.2. Distribution Characteristics of Microscopic Remaining Oil
3.2.1. NMR Technology
- (1)
- Experimental Method
- (2)
- Experimental Procedures
- Before the experiment, the rock core was cut to about 5 cm and dried at 110 °C to measure core length and diameter and physical parameters such as conventional porosity and permeability. The core was vacuumed, and the saturated formation water was pressurized. Then, the core was measured by NMR in saturated water T2 spectrum.
- Saturated oil and bound water, displacement speed of 0.1 mL/min, and co-displacement of about 15 pore volume were used (PV). The T2 spectrum of core was measured by NMR with saturated oil and bound water to record the volume of produced water and calculate the bound water saturation.
- The displacement speed of the water flooding was 0.1 mL/min, and no oil was produced at the producing side. The T2 spectrum of the core was measured using NMR at this state.
- After fracture flooding, surfactant displacement was performed through high-pressure and high-speed injection from the reverse direction (water flooding production side) with displacement pressure at 2 MPa and injection volume of 0.3 PV. The T2 spectrum of the core was measured using NMR at this state.
- (3)
- Distribution Characteristics of Microscopic Remaining oil NMR Results of Different Core Displacement Stages Are Shown in Figure 5:
3.2.2. Laser Scanning Confocal Technology
- (1)
- Experimental Method
- (2)
- Experimental Procedures
- Natural cores of class III reservoir in Daqing Oilfield (Table 3) were selected for core saturation at 45 °C.
- Water flooding: The core was flooded to 90% water content. The sample was made into thin slices. The remaining oil saturation, oil/water area, and different types of remaining oil of the sample were analyzed using computer image processing and confocal scanning laser technologies.
- Fracture-flooding: Surfactant (0.3 PV) was injected at the reverse high pressure (2 MPa) at the production side of water flooding. The remaining oil saturation, oil/water area, and remaining oil content of different types of samples were observed by confocal scanning laser technology.
Well Identifier | Core No. | Permeability (×10−3 μm2) | Porosity (%) | Bound Water Saturation (%) |
---|---|---|---|---|
G111-J455 | 1-2 | 106.5 | 24.03 | 34.77 |
N5-21-741 | 2-2 | 86.7 | 23.76 | 36.48 |
X2-1-729 | 3-2 | 121.6 | 24.65 | 33.56 |
- (3)
- Types and Distribution Characteristics of Remaining Oil
- (4)
- Analysis of Microscopic Remaining Oil Distribution in Different Displacement Stages
3.2.3. CT Scanning Technology
- (1)
- Experimental Method
- (2)
- Experimental Procedures
- Core preparation: Natural cores of class III reservoir layers were selected and dried at 110 °C, and core permeability, porosity, and other basic physical parameters were measured. After vacuumizing, the core was saturated with water first and then with oil. The CT scan was performed on the core in the initial bound water state to obtain the scanning data volume.
- Water flooding: The displacement speed was 0.1 mL/min. The displacement would be stopped when no oil was produced at the producing side. CT scan was performed on the core to obtain the scanning data volume.
- Fracture-flooding: Surfactant will be reversely injected at high pressure (2 MPa) to play a displacement role (injected at the production side of water flooding). Displacement speed was 0.6 mL/min, with an injection volume of 0.3 PV; the core was scanned by CT to obtain scan data volume.
- (3)
- Morphological Characterization of Microscopic Remaining Oil Occurrence
- Occurrence types of microscopic residual oil
- Distribution of remaining oil in the two-dimensional plane by CT scanning
- The construction of the three-dimensional model of remaining oil distribution after CT scanning
4. Conclusions and Suggestion
Author Contributions
Funding
Conflicts of Interest
References
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Well Identifier | Core No. | Permeability (×10−3 μm2) | Porosity (%) | Bound Water Saturation (%) |
---|---|---|---|---|
G111-J455 | 1-1 | 119.4 | 24.18 | 35.43 |
N5-21-741 | 2-1 | 103.5 | 22.46 | 35.04 |
X2-1-729 | 3-1 | 88.4 | 23.85 | 34.87 |
Core No. | Displacement State | Recovery Degree (%) | Absolute Recovery Degree (%) | Relative Recovery Degree (%) | ||||
---|---|---|---|---|---|---|---|---|
Small Pore (<10 ms) | Middle Pore (10–100 ms) | Macropore (>100 ms) | Small Pore (<10 ms) | Middle Pore (10–100 ms) | Macropore (>100 ms) | |||
1-1 | Water flooding | 35.94 | 3.14 | 13.89 | 18.91 | 18.63 | 32.08 | 44.42 |
Fracture-flooding | 52.84 | 6.93 | 22.08 | 23.83 | 41.22 | 51.61 | 54.68 | |
2-1 | Water flooding | 36.36 | 3.54 | 14.85 | 17.97 | 23.39 | 37.18 | 43.86 |
Fracture-flooding | 49.84 | 7.31 | 20.92 | 21.61 | 42.16 | 49.03 | 51.79 | |
3-1 | Water flooding | 33.38 | 5.19 | 12.83 | 15.36 | 15.26 | 30.16 | 41.85 |
Fracture-flooding | 48.56 | 9.23 | 19.08 | 20.25 | 39.34 | 47.57 | 53.46 | |
AVG | Water flooding | 35.23 | 3.96 | 13.86 | 17.41 | 19.09 | 33.14 | 43.38 |
Fracture-flooding | 50.41 | 7.82 | 20.69 | 21.90 | 40.91 | 49.40 | 53.31 |
Core No. | Displacement State | Recovery Degree (%) | So (%) | ||||||
---|---|---|---|---|---|---|---|---|---|
Bound Remaining Oil | Semi-Bound Remaining Oil | Free Remaining Oil | |||||||
Membrane- and Column-like Type Remaining Oil | Particle-Adsorbent-like Type | Slit-like Type | Corner-Shaped Type | Throat-like Type | Cluster-like Type | Intergranular-Adsorption-like Type | |||
1-2 | Water flooding | 35.94 | 10.24 | 7.08 | 2.20 | 3.16 | 1.59 | 15.53 | 5.91 |
Fracture-flooding | 52.84 | 6.13 | 5.88 | 1.65 | 2.02 | 1.03 | 13.25 | 4.32 | |
2-2 | Water flooding | 36.36 | 8.51 | 6.36 | 1.22 | 4.93 | 2.52 | 17.56 | 6.29 |
Fracture-flooding | 49.84 | 4.17 | 6.08 | 0.91 | 3.82 | 1.44 | 12.53 | 4.95 | |
3-2 | Water flooding | 33.38 | 7.91 | 5.96 | 2.68 | 5.35 | 2.96 | 14.17 | 5.26 |
Fracture-flooding | 48.56 | 4.54 | 5.52 | 2.09 | 4.12 | 1.89 | 11.84 | 4.25 | |
AVG | Water flooding | 35.23 | 8.89 | 6.47 | 2.03 | 4.48 | 2.36 | 15.75 | 5.82 |
Fracture-flooding | 50.41 | 4.95 | 5.83 | 1.55 | 3.32 | 1.45 | 12.54 | 4.51 |
Type | Typical Figure | Number of Occupied Pore-Throat | Shape Factor | Contact Ratio | Euler Number |
---|---|---|---|---|---|
clustered-like | Connected Pore Number > 5 | G > 2 | C ≥ 0.4 | EN ≤ −1 | |
multi-porous form | 1 < Connected Pore Number ≤ 5 | G > 2 | C ≥ 0.4 | EN > −1 | |
columnar-like | Number of Pore-Throat ≤ 1 | G > 2 | C ≥ 0.4 | EN > 0 | |
droplet-like | Number of Pore-Throat ≤ 1 | G ≤ 2 | C = 0 | EN > 0 | |
membranous-like | Thickness< 1/3 of pore-throat diameter | G > 2 | C < 0.4 | EN > 0 |
Well No. | Core No. | Displacement State | Oil Saturation, So (%) | Remaining Oil Saturation (%) | ||||
---|---|---|---|---|---|---|---|---|
Cluster-like | Multi-Porous Form | Column-like | Droplet-like | Membrane-like | ||||
G111-J455 | 1-3 | The initial | 68.72 | 38.68 | 18.89 | 1.56 | 5.14 | 4.45 |
Water flooding | 43.83 | 12.34 | 8.55 | 5.08 | 7.53 | 10.33 | ||
Fracture-flooding | 33.46 | 10.12 | 8.28 | 4.53 | 5.67 | 4.86 | ||
N5-21-741 | 2-3 | The initial | 65.61 | 32.41 | 23.46 | 3.59 | 3.98 | 2.17 |
Water flooding | 42.34 | 14.23 | 9.32 | 3.76 | 5.79 | 9.24 | ||
Fracture-flooding | 34.47 | 12.46 | 7.16 | 5.92 | 4.74 | 4.19 | ||
X2-1-729 | 3-3 | The initial | 67.11 | 33.95 | 24.76 | 2.62 | 3.03 | 2.75 |
Water flooding | 40.83 | 14.48 | 9.45 | 4.24 | 5.89 | 6.77 | ||
Fracture-flooding | 34.58 | 13.15 | 9.16 | 4.87 | 4.34 | 3.06 | ||
The mean | The initial | 67.15 | 35.01 | 22.37 | 2.59 | 4.05 | 3.12 | |
Water flooding | 42.33 | 13.68 | 9.11 | 4.36 | 6.40 | 8.78 | ||
Fracture-flooding | 34.17 | 11.91 | 8.20 | 5.11 | 4.92 | 4.04 |
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Jiang, N.; Zhang, Z.; Qu, G.; Zhi, J.; Zhang, R. Distribution Characteristics of Micro Remaining Oil of Class III Reservoirs after Fracture Flooding in Daqing Oilfield. Energies 2022, 15, 3385. https://doi.org/10.3390/en15093385
Jiang N, Zhang Z, Qu G, Zhi J, Zhang R. Distribution Characteristics of Micro Remaining Oil of Class III Reservoirs after Fracture Flooding in Daqing Oilfield. Energies. 2022; 15(9):3385. https://doi.org/10.3390/en15093385
Chicago/Turabian StyleJiang, Nan, Zilu Zhang, Guohui Qu, Jiqiang Zhi, and Rongzhou Zhang. 2022. "Distribution Characteristics of Micro Remaining Oil of Class III Reservoirs after Fracture Flooding in Daqing Oilfield" Energies 15, no. 9: 3385. https://doi.org/10.3390/en15093385