Patent ID: 11960046
Assignee: SAUDI ARABIAN OIL COMPANY
Field: Civil engineering (Other fields)
Classification: CPC E  G | IPC E  G

Claim 4:
5. A system, comprising:
a logging system coupled to a plurality of logging tools; and
a formation breakout simulator comprising a computer processor, wherein the formation breakout simulator is coupled to the logging system, the formation breakout simulator comprising functionality for:
setting an estimate SHmax of a maximum horizontal stress;
conducting an elastoplastic modeling simulation of a geological formation around a wellbore with the estimate SHmax and obtaining a simulated value ϕb,1 of a breakout angle, wherein the breakout angle is a half-width of a breakout region,
wherein conducting the elastoplastic modeling simulation comprises:
setting up a calculation region, wherein the calculation region has a boundary that corresponds to a wall of the wellbore;
setting a uniform stress condition for an entirety of the calculation region, wherein the uniform stress condition is represented by the estimate SHmax, a minimum horizontal stress, and a pore pressure of the geological formation at the depth; and
repeatedly reducing a normal stress that acts perpendicular to the boundary at the boundary by an amount while the uniform stress condition far away from the boundary is maintained and a shear stress at the boundary is maintained to be zero and calculating stress conditions in the calculation region until the normal stress at the boundary is substantially equal to a wellbore pressure above the pore pressure, and

wherein the estimate SHmax comprises calculating the estimate SHmax as, s
    Hmax
   
   =
   
    
     
      ucs
      +
      
       Δ
       ⁢
       
        P
        W
       
      
      +
      
       2
       ⁢
       
        P
        p
       
      
     
     
      1
      -
      
       2
       ⁢
       cos
       ⁢
       2
       ⁢
       
        θ
        b
       
      
     
    
    -
    
     
      S
      hmin
     
     ⁢
     
      
       1
       +
       
        2
        ⁢
        cos
        ⁢
        2
        ⁢
        
         θ
         b
        
       
      
      
       1
       -
       
        2
        ⁢
        cos
        ⁢
        2
        ⁢
        
         θ
         b
        
       
      
     
    
   
  
  ,, where

θb is equal to 90°−ϕb,m and obtained from a caliper log,
Pp is the pore pressure of the geological formation at the depth,
ΔPw is a wellbore pressure Pw at the depth above Pp,
Shmin is the minimum horizontal stress at the depth,
ucs is an unconfined compressive strength calculated as, ucs
   =
   
    
     2
     ⁢
     c
     ⁢
     cos
     ⁢
     φ
    
    
     1
     -
     
      sin
      ⁢
      φ
     
    
   
  
  ,
 

c is a cohesion of the geological formation at the depth, and
φ is a friction angle of the geological formation at the depth; and

upon determining that the simulated value ϕb,1 is greater than or equal to a prescribed value and is different from a measured breakout angle ϕb,m at the depth by more than a threshold value, repeatedly changing the estimate SHmax and conducting the elastoplastic modeling simulation.