Systems and methods for determining and/or using estimate of drilling efficiency

Patent metadata

Field	Value
Publication number	US-11230914-B2
Application number	US-201615548645-A
Country	US
Kind code	B2
Filing date	Feb 23, 2016
Priority date	Feb 23, 2015
Publication date	Jan 25, 2022
Grant date	Jan 25, 2022

Abstract

Systems and methods are provided for estimating and/or using drilling efficiency parameters of a drilling operation. A method for estimating drilling efficiency parameters may include using a borehole assembly that includes a drill bit to drill into a geological formation. A number of measurements of weight-on-bit and torque-on-bit may be obtained during a period in which weight-on-bit and torque-on-bit are non-steady-state. The measurements of weight-on-bit and torque-on-bit may be used to estimate one or more drilling efficiency parameters relating to the drilling of the geological formation during the period.

First claim

The invention claimed is:

1. A method for estimating a parameter related to drill bit wear during a subterranean drilling operation, the method comprising:
(a) rotating a drill bit in a wellbore to drill into a subterranean formation, the drill bit having an unknown bit wear;
(b) measuring a set of corresponding weight on bit (WOB) and torque on bit (TOB) values while rotating in (a), the set measured when WOB and TOB values ramp up from lower values after a pause in drilling or ramp down from higher values as drilling pauses, said measurements made at a frequency of at least 1 Hz during said ramp up or ramp down;
(c) fitting a nonlinear curve to a cross plot of the measured set of WOB and TOB values, the cross plot having TOB on the ordinate and WOB on the abscissa;
(d) evaluating the nonlinear curve to obtain the parameter related to drill bit wear, said evaluating including locating a steady state point in the nonlinear curve above which the curve is substantially linear, wherein the parameter related to drill bit wear is equal to a WOB value at the steady state point and is a product of a rock strength ε of the subterranean formation and an area of a wear flat A w , on the drill bit, the area of the wear flat being indicative of the drill bit wear;
(e) resuming drilling using a weight on bit above the WOB value at the steady state point;
(f) measuring a rate of penetration of drilling (ROP), a rotation rate of the drill bit (RPM), the TOB, and the WOB while drilling in (e);
(g) processing the ROP and the RPM measured in (f) and the parameter related to drill bit wear obtained in (d) to compute a modeled WOB and a modeled TOB at a plurality of estimated values of the area of the wear flat; and
(h) comparing the modeled WOB and the modeled TOB computed in (g) and the WOB and TOB measured in (f) at each of the values of the area of the wear flat to determine a likelihood of each area of the wear flat being correct.

2. The method of claim 1 , wherein (d) further comprises: further evaluating the nonlinear curve to determine at least one friction parameter related to a friction between the drill bit and the subterranean formation, the friction parameter determined by extrapolating said substantially linear portion of the nonlinear curve to the abscissa at which the WOB value is equal to εA w (1−μζ) wherein μζ represents the at least one friction parameter.

3. The method of claim 1 , further comprising:
obtaining an estimate of the rock strength ε from a logging measurement performed while drilling in (a); and
processing the obtained rock strength and the product obtained in (d) to compute the area of the wear flat.

4. The method of claim 1 , wherein:
at least a subset of the corresponding WOB and TOB values are measured in a downhole tool in (b),
said measurement frequency is higher than an immediately available data transfer rate of a telemetry system associated with the downhole tool;
the at least one of the WOB values and the TOB values measured in the downhole tool are transmitted to a surface location by the telemetry system during said resumed drilling in (e), wherein said fitting and said evaluating in (c) and (d) are performed at the surface location.

5. The method of claim 1 , further comprising:
(i) repeating (f), (g), and (h) at a plurality of depths in the wellbore to generate a matrix of likelihoods, the matrix of likelihoods being a two dimensional matrix of the likelihood values computed in (h) as a function of the depth and the area of the wear flat.

6. The method of claim 5 , wherein the matrix of likelihoods is computed using the following equation:

-

L
⁡

(

d
,

A
w

)

=



WOB
⁡

(
d
)

-

WOB

⁡

(

d
,

A
w

)



2

σ
W
2

+



TOB
⁡

(
d
)

-

TOB

⁢

(

d
,

A
w

)



2

σ
T
2

wherein L(d, A w ) represents the matrix of likelihoods at the plurality of depths d and the plurality of estimated values of the area of the wear flat A w , WOB (d) and TOB (d) represent the WOB and TOB values measured in (f), (d,A w ) and (d,A w ) represent the modelled WOB and the modelled TOB values computed in (g), and σ w and σ T represent measurement uncertainties for the WOB and TOB values measured in (f).

7. The method of claim 5 , further comprising:
(j) evaluating the matrix of likelihoods to determine a best fit path indicating a most likely bit wear as a function of depth in the wellbore.

8. The method of claim 1 , further comprising:
(i) processing the ROP, the RPM, the TOB, and the WOB measured in (f) in combination with an area of the wear flat having a highest likelihood of being correct to compute a formation strength.

Assignees

• Geoservices Equipements
• Schlumberger Technology Corp

Inventors

• Ringer Maurice
• Lessi Jacques
• Toussaint Charles

Classifications

• E21B44/00 Primary

  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

• E21B49/003

  by analysing drilling variables or conditions (E21B49/005 takes precedence; systems specially adapted for monitoring a plurality of drilling variables or conditions E21B44/00) · CPC title

• E21B47/18

  through the well fluid {, e.g. mud pressure pulse telemetry} · CPC title

• E21B47/13

  by electromagnetic energy, e.g. radio frequency · CPC title

• E21B47/00 Primary

  Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) · CPC title