Method and apparatus for casing thickness estimation

Patent metadata

Field	Value
Publication number	US-2016290123-A1
Application number	US-201415037843-A
Country	US
Kind code	A1
Filing date	Jan 2, 2014
Priority date	Jan 2, 2014
Publication date	Oct 6, 2016
Grant date	—

Abstract

Various embodiments include apparatus and methods to provide an estimation of casing wear. One method determines values of casing and drill string variables and constants. These constants and variables are used to dynamically generate an estimate of casing wear, based on a stress theory. The drilling operation can be halted when the estimate of casing wear reaches a predetermined value.

First claim

What is claimed is:

1 . A method comprising:
determining values of casing and drill string variables and constants; generating an estimate of casing wear based on the variables and constants; determining when the estimate of casing wear has reached a threshold; and stopping a drilling operation based on the estimate of casing wear reaching the threshold.

2 . The method of claim 1 , wherein determining the casing and drill string variables and constants comprises determining a load per unit width of a contacting element, a radii of curvature of the casing and a tool joint of the drill string, a modulii of elasticity of the casing and the tool joint of the drill string, and a Poisson's ratio of the casing and the tool joint of the drill string.

3 . The method of claim 2 , further comprising calculating the load per unit width of the contacting element based on an inclination and azimuth of the drill string.

4 . The method of claim 2 , further comprising estimating the casing wear by:

V
=

π0

.564


kF
n



D
tj



NLt


[

(

ρ
c

-

ρ
ij

)

ρ
c



ρ
tj

(

1
-

μ
c
2

E
c

)

+

(

1
-

v
tj
2

E
tj

)

]

1
2



inches
3



/


feet

where N=rotary speed (revolutions per minute), D tj =tool-joint diameter (inches), t=contact time (minutes), ρ c ,ρ tj =radii of curvature of the casing and the tool joint, respectively, E c , E tj =modulii of elasticity of the casing and the tool joint, respectively, and v c ,v tj =Poisson's ratio of the casing and the tool joint, respectively.

5 . The method of claim 4 , further comprising determining the contact time, t, by

t
=

L
×

L
tj

ROP
×

L
dp

minutes, where L=drilling distance (feet), L tj =drilling distance of the tool joint (feet), L dp =drilling distance of the drill string (feet); and ROP=rate of penetration into a geological formation (feet/minute).

6 . The method of claim 1 , further comprising reading data from downhole sensors during the drilling operation.

7 . The method of claim 6 , wherein determining when the estimate of casing wear has reached the threshold comprises:
dynamically updating the estimate of the casing wear in substantially real time using the data read from the downhole sensors; and comparing each updated estimate of casing wear to the threshold.

8 . A non-transitory machine-readable storage device having instructions stored thereon, which, when performed by a machine, cause the machine to perform operations, the operations comprising the method of claim 1 .

9 . A method comprising:
determining casing and drill string variables and constants comprising at least one of a load per unit width of a contacting element, a radii of curvature of the casing and a tool joint of a drill string, a modulii of elasticity of the casing and the tool joint of the drill string, and a Poisson's ratio of the casing and the tool joint of the drill string; generating a first estimate of casing wear prior to conducting a first drilling operation; conducting the first drilling operation and dynamically generating a second estimate of casing wear based on at least one of the variables and constants and downhole data; determining when the second estimate of casing wear has reached a predetermined value; and halting the first drilling operation based on the second estimate of casing wear reaching or exceeding the predetermined value.

10 . The method of claim 9 , further comprising reading the downhole data from sensors coupled to the drill string.

11 . The method of claim 9 , further comprising:
measuring actual casing wear after conducting the first drilling operation; and updating the first estimate of casing wear, prior to conducting a second drilling operation, based on the measured actual casing wear.

12 . The method of claim 11 , further comprising updating the first estimate of casing wear based on reading drilling data from logs of the first drilling operation.

13 . The method of claim 9 , wherein generating the second estimate is based on a formula which embodies Hertzian contact mechanics.

14 . A system comprising:
a sensor; and a cont

Assignees

• Landmark Graphics Corp

Inventors

• Samuel Robello

Classifications

• E21B44/00

  Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions · CPC title

• E21B47/007 Primary

  Measuring stresses in a pipe string or casing (for locating blocked portions of pipes E21B47/09) · CPC title

• E21B7/04

  Directional drilling · CPC title

• E21B49/006

  Measuring wall stresses in the borehole · CPC title

• E21B12/02 Primary

  Wear indicators · CPC title