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Biot's Coefficient

Biot's Coefficient



  • Understanding the poroelastic effect is of high interest for evaluating coupled effects of rock deformation and pore pressure during exploration, development and production operations. 

  • Important applications include time-dependent wellbore failure, predictions of fracture initiation and the evolution of pore pressure during development. 

  • Biot coefficient is an important poroelastic constant that dictates the coupled behavior and relates the magnitude of deformation of rock framework and fluid. 

  • Biot coefficient is critical for estimation of in situ minimum horizontal stress. 




The experiment requires to flow through the sample by varying the pore pressure and confining pressure and measuring the grain compressibility and bulk compressibility of the rock.  


Conventional rocks 

  • Brine is typically used as the pore fluid. 

  • The experiment is run at ambient temperature. 

  • In conventional rocks (high porosity), volumetric strain is used to characterize the poroelastic response of the rock. 


Unconventional rocks 

  • Use of supercritical fluids as the pore fluid to have access to the pore space. 

  • The experiment is run at least at 40 ºC to reach and maintain supercritical conditions. 

  • Pore pressure is greater than 2000 psi for supercritical conditions. 

  • Continuous real time P-wave velocity is used to characterize the poroelastic response of the rock since the volumetric strain as an indicator does not have enough resolution in tight rocks for estimating the Biot’s coefficient. 


Recommended Sample Dimensions: 

  • Diameter – 1 inch 

  • Length – 2 inches 

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