Abstract
The generation of a fracture network in reservoir rocks for fluids to flow via hydraulic fracturing is important in shale oil and gas development, and the intersection between hydraulic and natural fractures is key in bridging natural fractures. In this work, the intersection behaviors between hydraulic and natural fractures and fracture propagation in a three-dimensional (3D) space were investigated. A hydraulic fracturing lab facility is designed and a series of fracturing tests on eight underground cores from the Kong shale reservoir are carried out. First, visualization analysis was conducted on each sample before and after fracturing with the assistance of an X-ray CT scan and the following up 3D reconstruction. Second, an extension model of fracture intersection between natural and hydraulic fractures is established in 3D through analytical calculations. Finally, the intersection behaviors are classified into six zones according to our model analysis. Apart from interesting results and findings, insights into the formation and propagation of fracture networks are also provided, which are of great value in characterizing shale reservoirs.
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Abbreviations
- 3D:
-
Three-dimensional
- CT:
-
Computerized tomography
- HFs:
-
Hydraulic fractures
- NFs:
-
Natural fractures
- 2D:
-
Two-dimensional
- DA:
-
Dip angle
- AA:
-
Azimuth angle
- \({\tau }_{0}\) :
-
Shear stresses of natural fracture
- \({K}_{\mathrm{f}}\) :
-
Coefficient of friction
- Τ :
-
Shear stresses acting on NF
- \({\sigma }_{\mathrm{n}}\) :
-
Normal stresses acting on NF
- \({p}_{0}\) :
-
Pore pressure imposed on the NF surface
- \({\sigma }_{1}\) :
-
Maximum in-situ principle stress
- \({\upsigma }_{3}\) :
-
Minimum in-situ principle stress
- \({p}_{\sigma }\) :
-
Treatment overpressure
- \({T}_{0}\) :
-
Tensile stress
- b :
-
Coefficient
- \({\sigma }_{\mathrm{H}1}\) :
-
Stress along the HF plane and is perpendicular to the intersection line
- \({\sigma }_{\mathrm{v}1}\) :
-
Stress along the HF plane and the intersecting line
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This work was funded by the National Natural Science Foundation of China (project no. 51525404).
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Zhao, Z., Zhao, Y., Jiang, Z. et al. Investigation of Fracture Intersection Behaviors in Three-Dimensional Space Based on CT Scanning Experiments. Rock Mech Rock Eng 54, 5703–5713 (2021). https://doi.org/10.1007/s00603-021-02587-9
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DOI: https://doi.org/10.1007/s00603-021-02587-9