In-situ stress measurement method

Patent metadata

Field	Value
Publication number	US-11493393-B2
Application number	US-201716473407-A
Country	US
Kind code	B2
Filing date	Nov 6, 2017
Priority date	Dec 27, 2016
Publication date	Nov 8, 2022
Grant date	Nov 8, 2022

Abstract

An in-situ stress measurement method is provided. The method includes measuring a length of a maximum diameter at which an amount of distortion relative to a diameter of a standard circle of a measurement cross section of a boring core is largest and a length of a minimum diameter at which the amount of distortion relative to the diameter of the standard circle is smallest based on a shape of the measurement cross section of the boring core; measuring a length of a diameter in a vertical direction and a length of a diameter in a horizontal direction of the measurement cross section of a side-wall core acquired by hollowing ground in a well in an excavation direction thereof, based on a shape of the measurement cross section of the side-wall core; and calculating a maximum horizontal stress and a minimum horizontal stress by first and second equations.

First claim

The invention claimed is:

1. An in-situ stress measurement method for measuring three-dimensional stress elements acting on ground configuring the earth's crust, the method comprising:
excavating the ground to form a well;
acquiring a cylindrical boring core by hollowing a portion of the ground in the well located at a predetermined depth from the earth's surface out in an excavation direction of the well during the excavation of the well;
specifying a first angle (α) formed by an action direction of the maximum horizontal stress acting on the ground with respect to a standard orientation, which is an orientation of the maximum horizontal stress acting on the ground;
acquiring a cylindrical first side-wall core by hollowing the ground in the well located at the predetermined depth out from an inside surface of the well in a direction which is formed at a second angle (β 1 ) with respect to the standard orientation;
measuring a length of a maximum diameter (D max ) at which an amount of distortion relative to a diameter of a standard circle of a measurement cross section of the boring core is largest and a length of a minimum diameter (D min ) at which the amount of distortion relative to the diameter of the standard circle is smallest based on a shape of the measurement cross section of the boring core, wherein the measurement cross section of the boring core is set in a direction orthogonal to a longitudinal direction of the boring core;
measuring a length of a diameter (d1| ϕ=0 ) in a vertical direction of a measurement cross section of the first side-wall core and a length of a diameter (d1| ϕ=90 ) in a horizontal direction of the measurement cross section of the first side-wall core based on a shape of the measurement cross section of the first side-wall core, wherein the measurement cross section of the first side-wall core is set in a direction orthogonal to a longitudinal direction of the first side-wall core; and
calculating a maximum horizontal stress (S Hmax ) and a minimum horizontal stress (S hmin ) among the three-dimensional stress elements by first and second equations, wherein the first equation represents a differential stress (ΔS) between a maximum horizontal stress (S Hmax ) and a minimum horizontal stress (S hmin ) acting on the ground at the predetermined depth,

Δ
⁢
S

=

S
Hmax

-

S
hmin

=

E

1
+
v

·

D
max

-

D
min

D
min

wherein the second equation represents a differential stress (Δσ|β 1 ) between a horizontal stress (σ θ ) and a vertical stress (σ ν ) that act orthogonal to the longitudinal direction of the first side-wall core,

Δσ

|

β
1

=

1
2

⁢

(

S
Hmax

+

S
hmin

)

-

1
2

⁢

(

S
Hmax

-

S
hmin

)

⁢
cos
⁢

2
⁢

(

β
1

-
α

)

-

S
V

=

E

1
+
v

·

d
⁢
1

|

ϕ
=
90

-
d

⁢
1

|

ϕ
=
0

Assignees

• Japan Petroleum Exploration Co Ltd
• Univ Tohoku

Inventors

• Ito Takatoshi
• Tezuka Kazuhiko
• Tamagawa Tetsuya

Classifications

• G01L1/00 Primary

  Measuring force or stress, in general (measuring force due to impact G01L5/00) · CPC title

• G01N33/24

  Earth materials (G01N33/42 takes precedence) · CPC title

• G01L5/00 Primary

  Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes · CPC title

• E21B49/006

  Measuring wall stresses in the borehole · CPC title

• E21B49/06

  using side-wall drilling tools {pressing} or scrapers · CPC title