Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity
Volumetric fracture intensity (P<sub>32</sub>) is a parameter that plays a major role in the mechanical and hydraulic behaviour of rock masses. While methods such as Ground Penetrating Radar (GPR) are available to map the 3D geometrical characteristics of the fractures, the direct measur...
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| Format: | Article |
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MDPI AG
2023-06-01
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| Series: | Geosciences |
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| Online Access: | https://www.mdpi.com/2076-3263/13/6/187 |
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| author | Pedro Ojeda Davide Elmo Steve Rogers Andres Brzovic |
| author_facet | Pedro Ojeda Davide Elmo Steve Rogers Andres Brzovic |
| author_sort | Pedro Ojeda |
| collection | DOAJ |
| description | Volumetric fracture intensity (P<sub>32</sub>) is a parameter that plays a major role in the mechanical and hydraulic behaviour of rock masses. While methods such as Ground Penetrating Radar (GPR) are available to map the 3D geometrical characteristics of the fractures, the direct measurement of P<sub>32</sub> at a resolution compatible with geotechnical applications is not yet possible. As a result, P<sub>32</sub> can be estimated from the borehole and surface data using either simulation or analytical solutions. In this paper, we use Discrete Fracture Network (DFN) models to address the problem of estimating P<sub>32</sub> using information from boreholes (1D data). When calculating P<sub>32</sub> based on Terzaghi Weighting, it is common practice to use drill run lengths and limit the minimum angle between the borehole and the intersected fractures. The analysis presented in this paper indicated that limiting the minimum angle of intersection would result in an underestimation of the calculated P<sub>32</sub>. Additionally, the size of the interval has a significant impact on the variability of the calculated P<sub>32</sub>. We propose a methodology to calculate P<sub>32</sub> using variable lengths, depending on the angle between the fractures and the borehole. This methodology allows the capture of the spatial variation in intensity and simultaneously avoids artificially increasing or decreasing the intensity sampled along borehole intervals. Additionally, this work has addressed the impact of boundary effects in DFN models and proposes a methodology to mitigate them. |
| first_indexed | 2024-03-11T02:25:20Z |
| format | Article |
| id | doaj.art-5d16916ab9154537b268a13dd1e999ec |
| institution | Directory Open Access Journal |
| issn | 2076-3263 |
| language | English |
| last_indexed | 2024-03-11T02:25:20Z |
| publishDate | 2023-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Geosciences |
| spelling | doaj.art-5d16916ab9154537b268a13dd1e999ec2023-11-18T10:36:46ZengMDPI AGGeosciences2076-32632023-06-0113618710.3390/geosciences13060187Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture IntensityPedro Ojeda0Davide Elmo1Steve Rogers2Andres Brzovic3WSP, Vancouver, BC V6Z 2M1, CanadaNBK Institute of Mining Engineering, University of British Columbia, Vancouver, BC V6T 1Z4, CanadaWSP, Vancouver, BC V6Z 2M1, CanadaWSP, Vancouver, BC V6Z 2M1, CanadaVolumetric fracture intensity (P<sub>32</sub>) is a parameter that plays a major role in the mechanical and hydraulic behaviour of rock masses. While methods such as Ground Penetrating Radar (GPR) are available to map the 3D geometrical characteristics of the fractures, the direct measurement of P<sub>32</sub> at a resolution compatible with geotechnical applications is not yet possible. As a result, P<sub>32</sub> can be estimated from the borehole and surface data using either simulation or analytical solutions. In this paper, we use Discrete Fracture Network (DFN) models to address the problem of estimating P<sub>32</sub> using information from boreholes (1D data). When calculating P<sub>32</sub> based on Terzaghi Weighting, it is common practice to use drill run lengths and limit the minimum angle between the borehole and the intersected fractures. The analysis presented in this paper indicated that limiting the minimum angle of intersection would result in an underestimation of the calculated P<sub>32</sub>. Additionally, the size of the interval has a significant impact on the variability of the calculated P<sub>32</sub>. We propose a methodology to calculate P<sub>32</sub> using variable lengths, depending on the angle between the fractures and the borehole. This methodology allows the capture of the spatial variation in intensity and simultaneously avoids artificially increasing or decreasing the intensity sampled along borehole intervals. Additionally, this work has addressed the impact of boundary effects in DFN models and proposes a methodology to mitigate them.https://www.mdpi.com/2076-3263/13/6/187volumetric fracture intensitydiscrete fracture networkborehole databoundary effects |
| spellingShingle | Pedro Ojeda Davide Elmo Steve Rogers Andres Brzovic Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity Geosciences volumetric fracture intensity discrete fracture network borehole data boundary effects |
| title | Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity |
| title_full | Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity |
| title_fullStr | Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity |
| title_full_unstemmed | Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity |
| title_short | Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity |
| title_sort | discrete fracture network dfn analysis to quantify the reliability of borehole derived volumetric fracture intensity |
| topic | volumetric fracture intensity discrete fracture network borehole data boundary effects |
| url | https://www.mdpi.com/2076-3263/13/6/187 |
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