InterPore2021

Strength and stability of fractured rocks

2 Jun 2021, 15:45

15m

Oral Presentation (MS3) Flow, transport and mechanics in fractured porous media MS3

Speaker

Dr Srutarshi Pradhan (Researcher, PoreLab, NTNU)

Description

Strength and stability of rocks are essential information [1] for engineers and operators working in the field like petroleum production, geothermal installation and underground CO2 storage. During operations, sometimes fractures open-up at the well-boundaries and fractures are mostly seen as “disturbing elements” for the stability of wells and well-operations. It is a real challenge to plan a drilling operation in fractured-reservoirs (like chalk reservoirs) due to the presence of natural fracture network -drilling must be done in a controlled manner so that the well-integrity is not disturbed. Therefore, we need a better understanding on how pre-existing fractures can reduce the strength/stability of rocks. In addition, we need to develop tools for monitoring the opening-up of new fractures and their development. Our lab experiments [2,3] explored the stress-induced fracturing behavior of reservoir rocks during fluid injection scenarios. Using the acoustic emission (AE) monitoring system, we could count new fractures (micro-cracks) and track the major fracture propagation. In addition, we have developed a discrete element model (DEM) simulation code based on Fiber bundle model [4,5] to analyze the role of fractures (damage) on the strength/stability of porous rocks. Our simulation code can take into account both long-range and short-range load-sharing scenarios [6,7].

References

1. E. Fjær, R. M. Holt, P. Horsrud, A. M. Raaen and R. Risnes, Petrolum Related Rock Mechanics (Elsevier, 2008).
2. S. Pradhan, A. Stroisz, E. Fjær, J. Stenebråten, H.K. Lund and E. F. Sønstebø, “Stress-induced fracturing of reservoir rocks: Acoustic monitoring and mCT image analysis”, Int. J. of Rock Mechanics and Rock Engineering, DOI 10.1007/s00603-015-0853-4 (2015).
3. S. Pradhan, A. Stroisz, E. Fjær, J. Stenebråten, H.K. Lund, E. F. Sønstebø and S. Roy, “Fracturing tests on reservoir rocks: Analysis of AE events and radial strain evolution”, ARMA (2014).
4. S. Pradhan, A. Hansen and Bikas K. Chakrabarti, “Failure processes in elastic fiber bundles'', Rev. Mod. Phys. Vol. 82, No 1, 499-555 (2010).
5. A. Hansen, P. C. Hemmer and S. Pradhan, “The Fiber Bundle Model: Modeling Failure in Materials”, Wiley-VCH, Berlin (September 2015).
6. S. Pradhan, J. T. Kjellstadli and A. Hansen, “Variation of elastic energy shows reliable signal of upcoming catastrophic failure”, Front. Phys. Vol. 7 106 (2019).
7. J. T. Kjellstadli, E. Bering, M. Hendrik, S. Pradhan and A. Hansen, “Can Local Stress Enhancement Induce Stability in Fracture Processes? Part I: Apparent Stability”, Front. Phys. Vol. 7 105 (2019).

Presentation materials

Fractured-Rocks-final.pdf

Fractured-Rocks.pdf