Luo, M, Glover, PWJ orcid.org/0000-0003-1715-5474 and Pan, H (2019) A reassessment of the stress and natural fracture orientations from analysis of image logs in the Chinese Continental Scientific Drilling Program borehole at Donghai county, Jiangsu province, China. Journal of Asian Earth Sciences, 169. pp. 11-20. ISSN 1367-9120
Abstract
The Chinese Continental Scientific Drilling (CCSD) project has drilled a 5100 m deep research borehole in the Sulu ultra-high pressure (UHP) metamorphic belt, eastern China. The UHP metamorphic belt is thought to be a product of continent-continent collision and has consequently experienced very intensive structural deformation. Based on a more complete well log data set of CCSD borehole, we can have a more detailed and reliable study on the structure features of borehole wall and other rock physical properties than a previous study published in 2009. Abundant data related to borehole breakouts (BOs), drilling induced tensile fractures (DITFs) and natural fractures were collected from the image logs. The BO and DITF data indicate that the average direction of the maximum horizontal principal stress (SH) of the CCSD borehole site is about 79.2° which is consistent with the convergent direction (E-W) of the Pacific Sea Plate with respect to the Eurasian Plate. Analysis of DITFs indicated that in the case of the CCSD borehole, axial drilling induced tensile fractures (ADITFs) occur occasionally in the upper section (0–2300 m) of the borehole with low dipping angle (0–10°), while transverse drilling induced tensile fractures (TDITFs) occur significantly in the lower section (3800–5000 m) with high dipping angle (10–30°). The natural fracture distribution at depth in the metamorphic rocks of the CCSD borehole indicates that (1) the failure strength of rocks and borehole depth are two factors that affects natural fracture frequency, (2) most of the dip azimuth of natural fractures is consistent with the dip azimuth of foliations observed in the core, (3) the development of most of the natural fractures probably was dominated by the development of foliations, and both the natural fractures and foliations developed in response to the subduction and exhumation of the Sulu terrene.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018 Elsevier Ltd. This is an author produced version of a paper published in Journal of Asian Earth Sciences. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Continental deep drilling; Image logs; Stress orientation; Borehole breakout; Drilling induced tensile fracture; Natural fracture distribution |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Institute for Applied Geosciences (IAG) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 26 Oct 2018 13:28 |
Last Modified: | 25 Oct 2019 00:39 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.jseaes.2018.10.014 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:137796 |