10:45 〜 11:00
[SSS05-16] せん断増粘流体による岩石の多方向水圧破砕
★招待講演
キーワード：水圧破砕、き裂、地殻応力、レオロジー
In this study, we explored an innovative approach to hydraulic fracturing by employing shear thickening fluid (STF) as the fracturing fluid in uniaxial loading conditions. Unlike conventional hydraulic fracturing, which typically induces fractures along the orientation of maximum stress, our experiment aimed to induce fractures in multiple directions from the borehole.
STF, characterized as a non-Newtonian fluid with suspended particles in a solvent, exhibits viscosity changes in response to shear forces. By injecting STF into a 10 cm cubic granite specimen through a borehole and pressurizing the entire system, we observed hydraulic fracturing occurring at a significantly higher pressure (38 MPa) than the granite's tensile strength. Subsequent to the initial fracturing, borehole pressure dropped, followed by the observation of standard fracturing phenomena such as acoustic emissions (AEs).
Unexpectedly, after the initial fracturing, borehole pressure increased again, leading to several repeating breakdowns accompanied by AEs. Visual examination of the dismounted specimen revealed fractures propagating in different directions from the borehole. This multi-directional fracturing phenomenon was unique to the use of STF. Reference experiments using high viscous Newtonian fluid in the granite specimen failed to achieve similar results, confirming the reproducibility of the multi-directional hydraulic fracturing phenomenon with STF.
Our findings suggest that the ability of STF to alter its viscosity and potentially solidify within the nucleated fractures contributes to the observed multi-directional fracturing and the subsequent re-buildup of borehole pressure. This unconventional approach opens up new possibilities for enhancing permeability in formations through hydraulic fracturing in directions beyond the traditional maximum stress orientation.
STF, characterized as a non-Newtonian fluid with suspended particles in a solvent, exhibits viscosity changes in response to shear forces. By injecting STF into a 10 cm cubic granite specimen through a borehole and pressurizing the entire system, we observed hydraulic fracturing occurring at a significantly higher pressure (38 MPa) than the granite's tensile strength. Subsequent to the initial fracturing, borehole pressure dropped, followed by the observation of standard fracturing phenomena such as acoustic emissions (AEs).
Unexpectedly, after the initial fracturing, borehole pressure increased again, leading to several repeating breakdowns accompanied by AEs. Visual examination of the dismounted specimen revealed fractures propagating in different directions from the borehole. This multi-directional fracturing phenomenon was unique to the use of STF. Reference experiments using high viscous Newtonian fluid in the granite specimen failed to achieve similar results, confirming the reproducibility of the multi-directional hydraulic fracturing phenomenon with STF.
Our findings suggest that the ability of STF to alter its viscosity and potentially solidify within the nucleated fractures contributes to the observed multi-directional fracturing and the subsequent re-buildup of borehole pressure. This unconventional approach opens up new possibilities for enhancing permeability in formations through hydraulic fracturing in directions beyond the traditional maximum stress orientation.