Changes

====Borehole Slotting====

====Borehole Slotting====

Borehole slotting method involves cutting different 25-mm deep slots at the wall of a wellbore using a diamond saw. The cut slots form a half circle as shown in [[:File:GeoWikiWriteOff2021-Tayyib-Figure16.png|Figure 16]]. The strain changes before, during, and after cutting the slots, are measured using a sensor and converted into stress readings. This method helps avoid the high cost of using other in-situ measurement methods.  

Borehole slotting method involves cutting different 25-mm deep slots at the wall of a wellbore using a diamond saw. The cut slots form a half circle as shown in [[:File:GeoWikiWriteOff2021-Tayyib-Figure16.png|Figure 16]]. The strain changes before, during, and after cutting the slots, are measured using a sensor and converted into stress readings. This method helps avoid the high cost of using other in-situ measurement methods.  

[[File:GeoWikiWriteOff2021-Tayyib-Figure16.png|center|framed|{{Figure number|16}}Slots are cut into the wellbore in different direction (from Kanduth, et al.1991) [12]]]

[[File:GeoWikiWriteOff2021-Tayyib-Figure16.png|center|framed|{{Figure number|16}}Slots are cut into the wellbore in different direction (from Kanduth, et al.<ref>Kanduth, H., R. Corthesy, and D. Gill, 1991, Validation of borehole slotting as a method for in situ stress measurements: Paper presented at the 7th ISRM Congress, Aachen, Germany, September 1991.</ref>).]]

====Lab Based Core Sample Testing====

====Lab Based Core Sample Testing====

Cores are cylindrical rock samples that are collected during or after well drilling. They are sent to the laboratory for further testing. The Anelastic Strain Recovery (ASR) is a method used to determine the in-situ stresses and their orientation from cores by measuring the strain over time.

Cores are cylindrical rock samples that are collected during or after well drilling. They are sent to the laboratory for further testing. The Anelastic Strain Recovery (ASR) is a method used to determine the in-situ stresses and their orientation from cores by measuring the strain over time.

The core is placed in a container filled with silicon and the strain is monitored (see [[:File:GeoWikiWriteOff2021-Tayyib-Figure17.png|Figure 17]]). The change in the core dimension is related to the microcracks creation in the rock when in-situ stress is relieved. The alignment of these micro fractures depends on the direction of the principal stresses. When the stress is relieved, the core tends to expand most in the maximum stress relief direction, and least in the minimum stress relief direction. The volume of the microcracks is proportional to the values of the in-situ stresses.  

The core is placed in a container filled with silicon and the strain is monitored (see [[:File:GeoWikiWriteOff2021-Tayyib-Figure17.png|Figure 17]]). The change in the core dimension is related to the microcracks creation in the rock when in-situ stress is relieved. The alignment of these micro fractures depends on the direction of the principal stresses. When the stress is relieved, the core tends to expand most in the maximum stress relief direction, and least in the minimum stress relief direction. The volume of the microcracks is proportional to the values of the in-situ stresses.  

11  

11  

12 Kanduth, H., Corthesy, R., & Gill, D., 1991, Validation of borehole slotting as a method for, in situ stress measurements. Paper presented at the 7th ISRM Congress, Aachen, Germany, September 1991.

12  

13 Lin, W., Yeh, E., Ito, H., Hirono, T., Soh, W., Wang, C., Ma, K., Hung, J., & Song, S. (2007). Preliminary results of stress measurement using drill cores of TCDP hole-A: An application of anelastic strain recovery method to three-dimensional in-situ stress determination. Terrestrial, Atmospheric and Oceanic Sciences, v. 18, p. 379-393. doi:10.3319/TAO.2007.18.2.379(TCDP)

13 Lin, W., Yeh, E., Ito, H., Hirono, T., Soh, W., Wang, C., Ma, K., Hung, J., & Song, S. (2007). Preliminary results of stress measurement using drill cores of TCDP hole-A: An application of anelastic strain recovery method to three-dimensional in-situ stress determination. Terrestrial, Atmospheric and Oceanic Sciences, v. 18, p. 379-393. doi:10.3319/TAO.2007.18.2.379(TCDP)

14 Stacey, T., & Wesseloo, J., 1998, In situ stresses in mining areas in South Africa. South African Institute of Mining and Metallurgy, V. 98, P. 365-368.

14 Stacey, T., & Wesseloo, J., 1998, In situ stresses in mining areas in South Africa. South African Institute of Mining and Metallurgy, V. 98, P. 365-368.