Breakdown pressures due to infiltration and exclusion in finite length boreholes

Q. Gan, J. S. Alpern, Chris J. Marone, P. Connolly, Derek Elsworth

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Citations (Scopus)

Abstract

The theory of effective stress suggests that the breakdown pressure of a borehole should be a function of ambient stress and strength of the rock, alone. However, our experiments on finite boreholes indicate that the breakdown pressure is a strong function of fracturing fluid type/state as well. We explain reasons for this behavior including the roles of different fluid types and state in controlling the breakdown process. We propose that the fluid interfacial tension controls whether fluid invades pore space at the borehole wall and this in turn changes the local stress regime hence breakdown pressure. Interfacial tension is modulated by fluid state, as sub- or supercritical, and thus gas type and state influence the breakdown pressure. We develop expressions for the breakdown pressure in circular section boreholes of both infinite and finite length to validate our hypothesis. Importantly, the analysis accommodates the influence of fluid infiltration or exclusion into the borehole wall. For the development of a radial hydraulic fracture (longitudinal failure) the solutions are those of Detournay and Cheng (1992) and show a higher breakdown pressure for impermeable (Hubbert and Willis, 1957) relative to permeable (Haimson and Fairhurst, 1967). A similar difference in breakdown pressure exists for failure on a transverse fracture that is perpendicular to the borehole axis, in this case modulated by a parameterη = ν / (1-ν)α, where ν is Poisson ratio and α the Biot coefficient. A numerical solution is obtained for this finite length borehole to define tensile stresses at the borehole wall due to a decomposed loading from an external confining stress and interior pressurization. Numerical results agree with the breakdown pressure records recovered for experiments for pressurization by CO2 and argon:

Original languageEnglish (US)
Title of host publication47th US Rock Mechanics / Geomechanics Symposium 2013
Pages1374-1381
Number of pages8
StatePublished - Dec 1 2013
Event47th US Rock Mechanics / Geomechanics Symposium 2013 - San Francisco, CA, United States
Duration: Jun 23 2013Jun 26 2013

Publication series

Name47th US Rock Mechanics / Geomechanics Symposium 2013
Volume2

Other

Other47th US Rock Mechanics / Geomechanics Symposium 2013
CountryUnited States
CitySan Francisco, CA
Period6/23/136/26/13

Fingerprint

Boreholes
Infiltration
infiltration
borehole
fluid
Fluids
Pressurization
Surface tension
Fracturing fluids
tensile stress
Poisson ratio
pore space
argon
effective stress
Tensile stress
Argon
experiment
Experiments
Rocks
Hydraulics

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology

Cite this

Gan, Q., Alpern, J. S., Marone, C. J., Connolly, P., & Elsworth, D. (2013). Breakdown pressures due to infiltration and exclusion in finite length boreholes. In 47th US Rock Mechanics / Geomechanics Symposium 2013 (pp. 1374-1381). (47th US Rock Mechanics / Geomechanics Symposium 2013; Vol. 2).
Gan, Q. ; Alpern, J. S. ; Marone, Chris J. ; Connolly, P. ; Elsworth, Derek. / Breakdown pressures due to infiltration and exclusion in finite length boreholes. 47th US Rock Mechanics / Geomechanics Symposium 2013. 2013. pp. 1374-1381 (47th US Rock Mechanics / Geomechanics Symposium 2013).
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Gan, Q, Alpern, JS, Marone, CJ, Connolly, P & Elsworth, D 2013, Breakdown pressures due to infiltration and exclusion in finite length boreholes. in 47th US Rock Mechanics / Geomechanics Symposium 2013. 47th US Rock Mechanics / Geomechanics Symposium 2013, vol. 2, pp. 1374-1381, 47th US Rock Mechanics / Geomechanics Symposium 2013, San Francisco, CA, United States, 6/23/13.

Breakdown pressures due to infiltration and exclusion in finite length boreholes. / Gan, Q.; Alpern, J. S.; Marone, Chris J.; Connolly, P.; Elsworth, Derek.

47th US Rock Mechanics / Geomechanics Symposium 2013. 2013. p. 1374-1381 (47th US Rock Mechanics / Geomechanics Symposium 2013; Vol. 2).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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N2 - The theory of effective stress suggests that the breakdown pressure of a borehole should be a function of ambient stress and strength of the rock, alone. However, our experiments on finite boreholes indicate that the breakdown pressure is a strong function of fracturing fluid type/state as well. We explain reasons for this behavior including the roles of different fluid types and state in controlling the breakdown process. We propose that the fluid interfacial tension controls whether fluid invades pore space at the borehole wall and this in turn changes the local stress regime hence breakdown pressure. Interfacial tension is modulated by fluid state, as sub- or supercritical, and thus gas type and state influence the breakdown pressure. We develop expressions for the breakdown pressure in circular section boreholes of both infinite and finite length to validate our hypothesis. Importantly, the analysis accommodates the influence of fluid infiltration or exclusion into the borehole wall. For the development of a radial hydraulic fracture (longitudinal failure) the solutions are those of Detournay and Cheng (1992) and show a higher breakdown pressure for impermeable (Hubbert and Willis, 1957) relative to permeable (Haimson and Fairhurst, 1967). A similar difference in breakdown pressure exists for failure on a transverse fracture that is perpendicular to the borehole axis, in this case modulated by a parameterη = ν / (1-ν)α, where ν is Poisson ratio and α the Biot coefficient. A numerical solution is obtained for this finite length borehole to define tensile stresses at the borehole wall due to a decomposed loading from an external confining stress and interior pressurization. Numerical results agree with the breakdown pressure records recovered for experiments for pressurization by CO2 and argon:

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Gan Q, Alpern JS, Marone CJ, Connolly P, Elsworth D. Breakdown pressures due to infiltration and exclusion in finite length boreholes. In 47th US Rock Mechanics / Geomechanics Symposium 2013. 2013. p. 1374-1381. (47th US Rock Mechanics / Geomechanics Symposium 2013).