Agilent 5991-4754EN Measuring Stress-Strain Curves for Shale Rock by Dynamic Instrumented Indentation - Appl free download

File name 5991-4754EN Measuring Stress-Strain Curves for Shale Rock by Dynamic Instrumented Indentation - Appl

Keysight Technologies Measuring Stress-Strain Curves for Shale Rock by Dynamic Instrumented Indentation Application Note Abstract Three samples of shale rock, two from the Eagle Ford play, and one from the Haynesville play, were successfully tested by instrumented indentation. Results were remarkably repeatable, and hardness and Young's modulus were independent of force for test forces above 300mN. For the two samples from the Eagle Ford play, the reduced moduli were 54.3GPa and 40.6GPa, and the hardness values were 1.55GPa and 1.12GPa. For the Haynesville sample, the modulus was 22.5GPa and the hardness was 0.51GPa. By assuming a Poisson's ratio of 0.25 and negligible work hardening, stress-strain curves were deduced from these indentation measurements. Finite-element simulations of indentation experiments were conducted wherein the simulated materials were assigned the deduced stress-strain curves. Simulated force-displacement curves matched experimental force-displacement curves reasonably well, thus lending credibility to the material model and to the indentation method of determining constitutive properties. Introduction Shale formations host vast natural gas of plasticity. For isotropic materials, and oil reserves which are accessed by elasticity is fully described by the hydraulic fracturing. Experts in the oil Young's modulus and the Poisson's and gas industry have analytical tools at ratio, n. For stresses above the yield their disposal for optimizing fractures to stress, the material deforms plastically, maximize the productivity of a well, and exhibiting large strains for relatively these analytical tools require knowing small increases in stress. If the material the stress-strain curve for the shale, as has a capacity for work-hardening, then well as other mechanical properties. the stress-strain curve has a positive slope, F, beyond the yield point. If the The simplest elastic-plastic constitutive material has no capacity for work- model is illustrated schematically in hardening, then the stress-strain Figure 1 as a bi-linear stress-strain curve is flat beyond the yield point (F curve. Materials for which this model = 0). In summary, such materials are is appropriate experience elastic mechanically described by only four deformation so long as the principle parameters: Young's modulus (E), stress remains below the yield stress,