Hydraulic fracturing: Laboratory evidence of the brittle-to-ductile transition with depth

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Authors

Runhua Feng, Shuo Liu, Joel Sarout, Jeremie Dautriat, Zhiqi Zhong, Reza Rezaee, Mohammad Sarmadivaleh

Abstract

Understand the propagation of hydraulic fracture (HF) is essential for effectively stimulating the hydrocarbon production of unconventional reservoirs. Hydraulic fracturing may induce distinct failure modes within the formation, depending on the rheology of the solid and the in-situ stresses. A brittle-to-ductile transition of HF is thus anticipated with increasing depth, although only scarce data are available to support this hypothesis. Here we carry out laboratory hydraulic fracturing experiments in artificial geomaterials exhibiting a wide range of rheology: cubic samples 50x50x50 mm3 in size are subjected to true triaxial stresses with either a low (σv = 6.5 MPa, σH =3 MPa, and σh =1.5MPa), or a high (15 MPa, 10 MPa, and 5MPa) confinement. The 3D strains induced by hydraulic fracturing are monitored and interpreted; and X-ray Computed Tomography (CT) imaging is used to document the HF geometry. Finally, a correlation between the normalized fracture area (AFN) and the brittleness index (BI) of tested samples is introduced. Our results reveal that: (i)The intermediate stress plays a profound role in hydraulic fracture propagation subjected to the designed stress regimes (i.e., the transitional intermediate strain observed from brittle to ductile samples); (ii) The transitional inclined angle (high-to-low) of HFs are observed from brittle/semi-brittle samples to semi-ductile/ductile samples; (iii) The normalized fracture area (AFN) is shown to be larger when the BI is higher; the AFN, tortuosity and roughness of the HF are shown to be larger as the increase of confinement.

DOI

https://doi.org/10.31223/X5PH0S

Subjects

Earth Sciences, Engineering, Geology, Petroleum Engineering

Keywords

Hydraulic fracture propagation; Geometry of hydraulic fractures; Brittle-to-ductile transition; Fractured area; True triaxial stresses

Dates

Published: 2022-05-13 19:39

License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
The authors declare that they have no known competing interest

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