We are doing a project that focusses on hydraulic fracturing in wellbore, that is basically done to increase the production.
For that,
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We have created a 60 x 60 2D block (we are trying to simulate in 2D plane strain condition)
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We have created a partition in the middle of the block to incorporate zero thickness cohesive zone.
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Given the properties of matrix and that of the cohesive zone (We first assigned the partition as a cohesive layer in the mesh module)
Matrix:
(i) Elastic- Isotropic
Young’s Modulus: 627MPa
Poisson’s ratio: 0.31(ii) Fluid Leakoff
Top Coeff. = Bottom Coeff. = 1.786 * 10^-13(iii) Permeability
k= 1.24 * 10^-15 m^2 (1.24 mD)
Void Ratio= 0.3245Cohesive:
(i) Elastic- Traction
E/Enn = G1/Ess = G2/Ett = 100
(ii) Maxs Damage
Nominal Stress Normal Only Mode= 1.16*10^6 (tensile strength= 1.16MPa)
Nominal Stress First Direction= 2.32*10^6 (shear strength= 2.32MPa)
Nominal Stress Second Direction= 2.32*10^6
(iii) Damage Evolution
Displacement at failure= 0.0001m
(iv) Fluid Leakoff
Top Coeff. = Bottom Coeff. = 1.786 * 10^-13 -
Created a “Soils” step with a time period of 75s.
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In the load module:
(i) One predefined field was void ratio
(ii) Other was stress to simulate in-situ stresses ( x and y direction 3Mpa compressive)
Sigma 11= Sigma 22= -3e+06
Sigma 33= Sigma 12=0(iii) Load (flow rate) was applied in Step-1 in the center point (concentrated pore fluid with magnitude = 5*10^-4 m3/s)
(iv) Boundary conditions were also applied:
a) U1=0 ( for the extreme two bottom corners)
b) U2=0 (for lower edge) -
Coarse mesh was used.
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After evaluating job, we are getting following results:
We are not able to induce a crack as it should be in hydraulic fracturing.
What do you guys think can the reason for it be?
