Numerical simulation on borehole breakout and borehole size effect using discrete element method
Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries, although there are critical research gaps that remain unfilled. In this paper, numerical simulation is conducted on Gosford sandstone to investigate the borehole br...
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2020-09-01
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doaj-606075d784844bdb9b3948830ebda7c32020-11-25T03:55:39ZengElsevierInternational Journal of Mining Science and Technology2095-26862020-09-01305623633Numerical simulation on borehole breakout and borehole size effect using discrete element methodH. Lin0W.H. Kang1J. Oh2I. Canbulat3B. Hebblewhite4School of Minerals and Energy Resources Engineering, University of New South Wales, Sydney, NSW 2052, AustraliaCentre for Infrastructure Engineering, Western Sydney University, Penrith, NSW 2751, AustraliaSchool of Minerals and Energy Resources Engineering, University of New South Wales, Sydney, NSW 2052, Australia; Corresponding author.School of Minerals and Energy Resources Engineering, University of New South Wales, Sydney, NSW 2052, AustraliaSchool of Minerals and Energy Resources Engineering, University of New South Wales, Sydney, NSW 2052, AustraliaEstimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries, although there are critical research gaps that remain unfilled. In this paper, numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect, including temperature influence. The discrete element method (DEM) model shows that the borehole breakout angular span is constant after the initial formation, whereas its depth propagates along the minimum horizontal stress direction. This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation. The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking. This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock. In addition, the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells. Based on the results, the higher temperature led to lower breakout initiation stress with same borehole size, and more proportion of shear cracks was generated under higher temperature. This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries. Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions, suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.http://www.sciencedirect.com/science/article/pii/S2095268620300367Borehole breakoutBreakout angular spanBorehole size effectNumerical simulationThermal effect |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
H. Lin W.H. Kang J. Oh I. Canbulat B. Hebblewhite |
spellingShingle |
H. Lin W.H. Kang J. Oh I. Canbulat B. Hebblewhite Numerical simulation on borehole breakout and borehole size effect using discrete element method International Journal of Mining Science and Technology Borehole breakout Breakout angular span Borehole size effect Numerical simulation Thermal effect |
author_facet |
H. Lin W.H. Kang J. Oh I. Canbulat B. Hebblewhite |
author_sort |
H. Lin |
title |
Numerical simulation on borehole breakout and borehole size effect using discrete element method |
title_short |
Numerical simulation on borehole breakout and borehole size effect using discrete element method |
title_full |
Numerical simulation on borehole breakout and borehole size effect using discrete element method |
title_fullStr |
Numerical simulation on borehole breakout and borehole size effect using discrete element method |
title_full_unstemmed |
Numerical simulation on borehole breakout and borehole size effect using discrete element method |
title_sort |
numerical simulation on borehole breakout and borehole size effect using discrete element method |
publisher |
Elsevier |
series |
International Journal of Mining Science and Technology |
issn |
2095-2686 |
publishDate |
2020-09-01 |
description |
Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries, although there are critical research gaps that remain unfilled. In this paper, numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect, including temperature influence. The discrete element method (DEM) model shows that the borehole breakout angular span is constant after the initial formation, whereas its depth propagates along the minimum horizontal stress direction. This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation. The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking. This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock. In addition, the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells. Based on the results, the higher temperature led to lower breakout initiation stress with same borehole size, and more proportion of shear cracks was generated under higher temperature. This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries. Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions, suggesting that the temperature may need to be considered for breakout stress analysis in deep locations. |
topic |
Borehole breakout Breakout angular span Borehole size effect Numerical simulation Thermal effect |
url |
http://www.sciencedirect.com/science/article/pii/S2095268620300367 |
work_keys_str_mv |
AT hlin numericalsimulationonboreholebreakoutandboreholesizeeffectusingdiscreteelementmethod AT whkang numericalsimulationonboreholebreakoutandboreholesizeeffectusingdiscreteelementmethod AT joh numericalsimulationonboreholebreakoutandboreholesizeeffectusingdiscreteelementmethod AT icanbulat numericalsimulationonboreholebreakoutandboreholesizeeffectusingdiscreteelementmethod AT bhebblewhite numericalsimulationonboreholebreakoutandboreholesizeeffectusingdiscreteelementmethod |
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