Prediction on Fused Silica Surrogate Cylindrical Samples Varun Gupta 508 mm 16 mm 254 mm 32 mm Geometry and Material Properties Material Fused Quartz Assumptions Linear Elastic material behavior is assumed with the following properties ID: 1048536
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1. Numerical Modeling for Hydraulic Fracture Predictionon Fused Silica Surrogate Cylindrical SamplesVarun Gupta
2. 50.8 mm16 mm25.4 mm3.2 mmGeometry and Material PropertiesMaterial: Fused Quartz Assumptions:Linear Elastic material behavior is assumed with the following properties:Young’s Modulus = 74 GpaPoisson’s Ratio = 0.17Fracture Toughness = 0.65-0.70 MPa m0.5 Thermo-mechanical effects are not consideredGoal: To predict overpressures required to fracture an homogeneous pure (surrogate) material with known mechanical properties to compare these values to experimental overpressures obtained in our lab-scale stimulation system.
3. Numerical Model: Loading and BCsFixedPext = 5000 psiPint = 6000-9000 psiModeled as an axisymmetric problemConstant confining pressure of 5000 psi is appliedInternal pressure is applied incrementallyQuantity of interest: Fracture parameters near the cornerObjective is to determine the internal pressure which leads to fracture
4. Number of elements: 44915Number of nodes: 136066Quadratic quadrilateral elements are usedLocalized refinement performed close to the cornerMesh Details and Stress distributionMaximum in-plane principal stress at Pint = 9000 psi
5. Direction of crack extensionθMaximum energy release rate is attained at an angle of 45°, which is the angle of crack initiation
6. Stress Intensity Factor vs Internal PressureGiven the fracture toughness of KIC = 0.7 Mpa m0.5 , at 5000 psi confining pressure the fracture is predicted at Pint ~ 8500 psi, i.e., overpressure = 3500psi
7. Effect of Different Confining PressureConfining pressure does not seem to have a significant role in the fracturing overpressure.
8. Smoothed cornerR 0.1mmSmoothing the corner out averts failure until much higher loadFor example, introducing 0.1 mm fillet radius increases the fractureoverpressure to ~10,600 psi