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US 11,960,046 B2Granted
Method for determining in-situ maximum horizontal stress
AssigneeSaudi Arabian Oil Company
InventorYanhui Han
Life of this patent
Estimating the term…
Abstract
A method for obtaining a maximum horizontal stress at a depth of a geological formation, includes: setting an estimate SHmax of the maximum horizontal stress; conducting an elastoplastic modeling simulation of the 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; and upon determining that the estimate 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.
Claims11
A method for obtaining a maximum horizontal stress at a depth of a geological formation, comprising:
- setting an estimate SHmax of the maximum horizontal stress;
- conducting an elastoplastic modeling simulation of the 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.
79 more elements
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.
82 more elements
A non-transitory computer readable medium storing instructions executable by a computer processor, the instructions 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.
80 more elements
Dependencies are inferred from the claim text.