Investigation on Energy Enhancement of Shale Oil Imbibition Under Different Fracture Fluid Injection Methods—A Case Investigation of Jimsar Lucaogou Formation
Abstract
:1. Introduction
2. Experiment and Methods
2.1. Experimental Equipment
2.2. Materials
2.3. Experimental Methods
3. Energy Storage Effect of Fracturing Fluid
3.1. Energy Storage Effect Law
3.2. The Influence of Energy Storage on Porosity and Permeability
4. Optimization of CO2 Injection Volume and Well Shut-In Time
4.1. CO2 Pre-Injection Optimization
4.2. Optimization of Well Shut-In Time
5. Characteristics of Imbibition During the Energy Storage Period
6. Conclusions
- By measuring and comparing the pore permeability characteristics of the Jimsar core before and after energy storage, it was found that different fracturing fluids showed varying degrees of improvement in porosity and permeability after energy storage. Among them, CO2 pre-dissolved in the sliding water can be more dissolved in the sliding water, increasing the permeability of the rock core by about 1.26 times and the porosity by 11.4%. The pre-shut-in time of the sliding water can be appropriately extended to achieve the dissolution effect.
- The energy storage effects of four fracturing fluids were compared, namely pure CO2, CO2 pre-fracturing fluid, sliding water pre-fracturing fluid, and pure sliding water fracturing fluid. The results showed that, due to the high expansion coefficient and low interfacial tension of pure CO2, the energy storage effect of pure CO2 was the best, with an energy storage pressure of up to 7.85 MPa. The energy storage effect of pure sliding water fracturing fluid was the opposite, with an energy storage pressure of only 2.45 MPa.
- Considering factors such as comprehensive economy and energy storage efficiency, the optimal range for CO2 pre-load is between 20% and 30%. Based on a CO2 density of 770 kg/m3 (20 °C) and a single-stage fracturing fluid consumption of 2000 m3, it is recommended to use 308 t–462 t of on-site single-stage CO2 pretreatment.
- Based on the optimization criterion of energy storage pressure balance, the optimal shut-in time for CO2 should be 5 h and for slickwater 12.8 h.
- Compared with different types of fracturing fluids, CO2 can effectively utilize small pore crude oil in rock cores, while more mesopore crude oil is utilized on the basis of energy storage. The recovery of imbibition is about 29%, which is about 10% higher than that of slickwater.
- This research can provide assistance in determining the CO2 pre-injection and well shut-in time of the Jimsar Lucaogou Formation well area. The results provide theoretical support for energy storage fracturing construction in other shale oil reservoirs of the same type.
- This article has not yet given detailed consideration to the simulation of crack complexity setting and backflow stage after well shut-in. Subsequently, integrated experimental analysis of fracturing, shut-in, and backflow can be conducted on the full diameter scale physical model to obtain full life cycle analysis data of rock cores containing artificial fractures.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Field-Scale (Single Stage) | Experimental Scale | |||
---|---|---|---|---|
Parameters | Near Fracture | Far Fracture | Parameters | Core sample |
Fracture length (Lf)/m | 260 | 260 | Core length (L)/cm | 6 |
Fracture height (hf)/m | 24 | 24 | Core radius (r)/cm | 1.25 |
Clusters (n) | 5 | 5 | Porosity (φ)/% | 13 |
Half-cluster spacing (Cf)/m | 0.06 | 3.94 | Calculation formula | L × π × r2 × φ |
Porosity (φ)/% | 13 | 13 | Crude oil volume/cm3 | 3.82 |
Calculation formula | Lf × hf × n × Cf × φ × 2 | Fracturing fluid/cm3 | 16 | |
Crude oil volume/m3 | 486.72 | 31,961.28 | Remote crude oil volume/cm3 | 256 |
Fracturing fluid: Near fracture crude oil: Remote crude oil | 2000:486.72:31,961.28 ≈4:1:64 | Fracturing fluid: Near fracture crude oil: Remote crude oil | 15.5:3.82:244 ≈4:1:64 |
Core | Mass/g | Diameter/cm | Length/cm | Lithology | Permeability/mD | Porosity/% |
---|---|---|---|---|---|---|
J0 | 54.25 | 2.47 | 5 | Grey mudstone sandstone | 0.15 | 14.45 |
J1 | 53.35 | 2.53 | 5 | Grey mudstone sandstone | 0.16 | 16.49 |
J2 | 53.27 | 2.50 | 5 | Grey mudstone sandstone | 0.141 | 15.58 |
J3 | 53.64 | 2.51 | 5 | Grey mudstone sandstone | 0.158 | 15.79 |
J4 | 53.38 | 2.52 | 5 | Grey mudstone sandstone | 0.132 | 11.85 |
J5 | 53.22 | 2.50 | 5 | Grey mudstone sandstone | 0.096 | 16.41 |
J6 | 53.15 | 2.50 | 5 | Grey mudstone sandstone | 0.073 | 13.22 |
Core Number | Experimental Scheme | Energy Storage Method |
---|---|---|
J0 | Tradition | 10 MPa slickwater |
J1 | Pure Slickwater | 10 MPa slickwater |
J2 | Pre-Slickwater | 5 MPa slickwater + 5 MPa CO2 |
J3 | Pure CO2 | 10 MPa CO2 |
J4 | Pre-CO2 | 5 MPa CO2 + 5 MPa slickwater |
J5 | 3 MPa CO2 + 7 MPa slickwater | |
J6 | 1 MPa CO2 + 9 MPa slickwater |
Core Number | Experimental Scheme | Initial Permeability/mD | Post-Experiment Permeability/mD | Growth Rate/% | Initial Porosity/% | Post-Experiment Porosity/% | Growth Rate/% |
---|---|---|---|---|---|---|---|
J1 | Pure Slickwater | 0.16 | 0.166 | 3.8 | 16.49 | 16.71 | 1.35 |
J2 | Pre-Slickwater | 0.141 | 0.320 | 126.6 | 15.58 | 17.36 | 11.4 |
J3 | Pure CO2 | 0.158 | 0.180 | 13.9 | 15.79 | 16.08 | 1.83 |
J4 | 5 MPa CO2 + 5 MPa slickwater | 0.132 | 0.148 | 12 | 11.85 | 11.99 | 1.15 |
Core Number | Experimental Scheme | Imbibition Recovery, % | Lower Limit of Pore Utilization, μm |
---|---|---|---|
J1 | slickwater | 20.4 | 0.02525 |
J2 | pre-slickwater | 18.5 | 0.02579 |
J3 | CO2 | 30.5 | 0.02501 |
J4 | pre-CO2 | 28.5 | 0.02509 |
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Zhu, J.; Wang, F.; Wang, J.; Li, Z.; Zhang, S. Investigation on Energy Enhancement of Shale Oil Imbibition Under Different Fracture Fluid Injection Methods—A Case Investigation of Jimsar Lucaogou Formation. Energies 2025, 18, 1412. https://doi.org/10.3390/en18061412
Zhu J, Wang F, Wang J, Li Z, Zhang S. Investigation on Energy Enhancement of Shale Oil Imbibition Under Different Fracture Fluid Injection Methods—A Case Investigation of Jimsar Lucaogou Formation. Energies. 2025; 18(6):1412. https://doi.org/10.3390/en18061412
Chicago/Turabian StyleZhu, Jian, Fei Wang, Junchao Wang, Zhanjie Li, and Shicheng Zhang. 2025. "Investigation on Energy Enhancement of Shale Oil Imbibition Under Different Fracture Fluid Injection Methods—A Case Investigation of Jimsar Lucaogou Formation" Energies 18, no. 6: 1412. https://doi.org/10.3390/en18061412
APA StyleZhu, J., Wang, F., Wang, J., Li, Z., & Zhang, S. (2025). Investigation on Energy Enhancement of Shale Oil Imbibition Under Different Fracture Fluid Injection Methods—A Case Investigation of Jimsar Lucaogou Formation. Energies, 18(6), 1412. https://doi.org/10.3390/en18061412