Thermal e�ects on wellbore stress

Strongly time dependent

strongly depenendent of the silica content of the rock.

Under steady-state conditions,

Time-temperature e�ects

© Cambridge University Press (Fig. 6.14a,b pp. 194)Zoback, Reservoir Geomechanics

Stability through cooling?

Cooling Reference

© Cambridge University Press (Fig. 6.14c pp. 194 and Fig. 6.3pp. 173)

Zoback, Reservoir Geomechanics

Rock strength anisotropy

© Cambridge University Press (Fig. 4.12, pp. 106)Zoback, Reservoir Geomechanics

Rock strength anisotropy e�ects onbreakouts

© Cambridge University Press (Fig. 6.16a,b pp. 199)Zoback, Reservoir Geomechanics

Two mechanisms

Stresses exceed intact rock strengthStresses activate slip on weak bedding planes

© Cambridge University Press (Fig. 6.16c pp. 199)Zoback, Reservoir Geomechanics

Chemical e�ectsWater Activity ( ) can to increased pore pressure

from breakout data

Example

© Cambridge University Press (Fig. 7.7 pp. 223)Zoback, Reservoir Geomechanics

Wellbore stability

De�ning a "stable" wellbore

© Cambridge University Press (Fig. 10.1a,b pp. 304)Zoback, Reservoir Geomechanics

Emperical model: Maximum 90breakouts

© Cambridge University Press (Fig. 10.2a,b pp. 305)Zoback, Reservoir Geomechanics

Comprehensive model

Design based on pore pressure and frac gradient

Model considering collapse pressure Final design

© Cambridge University Press (Fig. 10.3a,b,c pp. 307)Zoback, Reservoir Geomechanics