THE 3
rd
INTERNATIONAL SCIENTIFIC CONFERENCES OF STUDENTS AND YOUNG RESEARCHERS
dedicated to the 99
th
anniversary of the National Leader of Azerbaijan Heydar Aliyev
79
Figure 1.
First
stage-shale conditions
Figure 2.
Second stage-shale conditions
before drilling after drilling
The
third stage occurs when
additional water moves into the clays in
the shale. Swelling stresses are
developed until failure occurs and shale
cavings
are produced, resulting in
wellbore
enlargement (Figure 3).
Based on thermoelasticity theory, a
quantification model of hydration effect
was created by H. Rongzun, et al., and
Yew, et al.
which ascribes hydration
alterations to total water volume. In this
method, rock expansion strain is defined
only by water volume. It is not about the
significance of chemical interaction
between drilling mud and shale. Hale et
al. used
semi-permeable membrane
equivalent pore pressure theory on the
interaction between WBM and shale.
The effect of water influx due to pressure differences in the shale was
disclaimed. Also, the effects of ion diffusion and exchange on shale hydration
were refused. According to the thermodynamic law and Gibbs-Duhem
equation, the coupling model of suction expansion is created by Heidug et
al. In this model, the osmosis, expansion, and solute penetration between
water phase in the drilling mud and pore water in shale is supposed. This
method does not assume the joint effect of pore pressure of fluid and rock
deformation. Ghassemi, et al. created a linear
chemistry-pore elasticity
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