# US 2023/0054050 A1 · Calibration of drillstring weight with drag for friction factor estimation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0054050 A1 - Document ID: US20230054050A1 - Status: Published application - Kind: A1 - Application number: 17/445,582 - Filed: 2021-08-20 - Published: 2023-02-23 - Earliest claimed: 2021-08-20 - Assignees: Landmark Graphics Corporation - Applicants: Landmark Graphics Corporation - Inventors: Robello Samuel - Web page: https://patentgrep.com/patent/US20230054050A1 ## CPC - E21B 44/00: 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 - E21B 47/007: Measuring stresses in a pipe string or casing (for locating blocked portions of pipes E21B47/09) - E21B 12/00: Accessories for drilling tools - G01N 19/02: Measuring coefficient of friction between materials {(testing of tyres G01M17/02; determinations of friction coefficient used in vehicle braking or traction control systems B60T8/172)} - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A method comprises determining a value of at least one oppositional force for a drillstring at multiple depths in the wellbore, determining a value of a drag force for the drillstring at the multiple depths, determining a value of hook load for the drillstring at the multiple depths based on the value of the at least one opposition force and the value of the drag force at the multiple depths, and determining a calibrated drillstring weight based on a change in the value of the hook load over the multiple depths. From the calibrated drillstring weight, an adjusted estimated hook load can be determined. The drag force can be calculated based on a drag per centralizer and the number of centralizers in the wellbore. A centralizer friction factor can be determined and used to calibrate the value of the drag per centralizer. ## Claims ### Claim 1 A method comprising: determining a value of at least one oppositional force for a drillstring at multiple depths in a wellbore, wherein the at least one oppositional force includes a centralizer friction force based on the presence of one or more centralizers positioned within the wellbore; determining a value of hook load for the drillstring at the multiple depths in the wellbore based at least in part on the value of the at least one oppositional force; determining a calibrated drillstring weight based on a change of the value of hook load for the drillstring over the multiple depths in the wellbore; determining a friction factor based on calibrated drillstring weight; and controlling one or more drilling operations performed on the wellbore based at least in part on the friction factor. ### Claim 2 (depends on 1) The method of claim 1, wherein determining the value of hook load for the drillstring comprises determining a value of a measured hook load for the drillstring at the multiple depths based on the value of the at least one oppositional force, and determining a value of an estimated hook load for the drillstring at the multiple depths based on the value of the at least one oppositional force, and wherein determining the calibrated drillstring weight comprises determining the calibrated drillstring weight is based on a change in the measured hook load and a change in the estimated hook load. ### Claim 3 (depends on 2) The method of claim 2, wherein determining the value of the estimated hook load further comprises determining an adjusted drillstring weight at the multiple depths in the wellbore based on the value of the at least one oppositional force, and the value of the estimated hook load, and wherein determining the calibrated drillstring weight comprises determining the calibrated drillstring weight based on a change in the measured hook load and a change in the adjusted drillstring weight. ### Claim 4 (depends on 1) The method of claim 1, further comprising: determining a value of an adjusted estimated hook load for the drillstring at the multiple depths in the wellbore based on the calibrated drillstring weight, wherein determining the value of the adjusted estimated hook load comprises determining the value of the adjusted estimated hook load based on the calibrated drillstring weight, and the value of the at least one oppositional force at the multiple depths in the wellbore. ### Claim 5 (depends on 1) The method of claim 1, wherein determining the calibrated drillstring weight based on a change in the value of hook load for the drillstring over the multiple depths in the wellbore comprises determining a rate of change of the value of hook load over at least two of the multiple depths in the wellbore. ### Claim 6 (depends on 5) The method of claim 5, wherein the at least two of the multiple depths in the wellbore comprise a first depth in the wellbore before addition of a first centralizer to the wellbore and a second depth in the wellbore after addition of the first centralizer to the wellbore. ### Claim 7 (depends on 1) The method of claim 1, wherein the at least one oppositional force includes a centralizer running drag based on a number of the one or more centralizers positioned within the wellbore and a set of drag per centralizer values. ### Claim 8 (depends on 7) The method of claim 7, wherein the set of drag per centralizer values is approximated from one or more manufacturer specifications. ### Claim 9 (depends on 1) The method of claim 1, wherein determining the friction factor further comprising: determining a first friction factor for the drillstring for a first depth in the wellbore based on a first calibrated drillstring weight, the value of hook load, the value of the at least one oppositional force, wherein determining the first calibrated drillstring weight comprises determining the calibrated drillstring weight for the first depth in the wellbore. ### Claim 10 (depends on 9) The method of claim 9, further comprising: determining a second friction factor for the drillstring for a second depth in the wellbore based on a second calibrated drillstring weight, the value of hook load, and the value of the at least one oppositional force, wherein determining the second calibrated drillstring weight comprises determining the calibrated drillstring weight for the second depth in the wellbore. ### Claim 11 (depends on 10) The method of claim 10, wherein the wellbore is substantially vertical at the first depth and the second depth. ### Claim 12 (depends on 10) The method of claim 10, further comprising: determining whether the friction factor increases as a function of a number of the one or more centralizers positioned in the wellbore at the first depth and a number of the one or more centralizers positioned in the wellbore at the second depth and on the first friction factor and the second friction factor; and based on a determination that the friction factor increases as a function of the number of centralizers in the wellbore, increasing a value of drag per centralizer determining a value of running drag for the drillstring based on the number of the one or more centralizers positioned in the wellbore and the value of drag per centralizer. ### Claim 13 (depends on 10) The method of claim 10, further comprising: determining whether the friction factor decreases as a function of a number of the one or more centralizers positioned in the wellbore based on a number of centralizers in the wellbore at the first depth and a number of centralizers in the wellbore at the second depth and on the first friction factor and the second friction factor; and based on a determination that the friction factor decreases as a function of the number of centralizers in the wellbore, decreasing a value of drag per centralizer. ### Claim 14 One or more non-transitory machine-readable media comprising program code for drillstring weight calibration, the program code to: determine a value of at least one oppositional force for a drillstring at multiple depths in a wellbore, wherein the at least one oppositional force includes a centralizer friction force based on the presence of one or more centralizers positioned within the wellbore; determine a value of hook load for the drillstring at the multiple depths in the wellbore based at least in part on the value of the at least one oppositional force; and determine a calibrated drillstring weight based on a change of the value of hook load for the drillstring over the multiple depths in the wellbore; determine a friction factor based on calibrated drillstring weight; and control one or more drilling operations performed on the wellbore based at least in part on the friction factor. ### Claim 15 (depends on 14) The one or more non-transitory machine-readable media of claim 14, wherein program code to determine the calibrated drillstring weight comprises program code to: determine a rate of change of the value of hook load over at least two of the multiple depths in the wellbore. ### Claim 16 (depends on 15) The one or more non-transitory machine-readable media of claim 15, the at least two of the multiple depths in the wellbore comprise a first depth in the wellbore before addition of a first centralizer to the wellbore and a second depth in the wellbore after addition of the first centralizer to the wellbore. ### Claim 17 (depends on 14) The one or more non-transitory machine-readable media of claim 14, further comprising program code to: determine a first friction factor for the drillstring for a first depth in the wellbore based on a first calibrated drillstring weight, the value of hook load, and the value of the at least one oppositional force, wherein determining a first calibrated drillstring weight comprises determining the calibrated drillstring weight for the first depth in the wellbore; determine a second friction factor for the drillstring for a second depth in the wellbore based on a second calibrated drillstring weight, the value of hook load, the value of the at least one oppositional force, wherein determining the second calibrated drillstring weight comprises determining the calibrated drillstring weight for the second depth in the wellbore; and determine whether a friction factor increases as a function of a number of centralizers in the wellbore based a number of centralizers in the wellbore at the first depth and a number of centralizers in the wellbore at the second depth and on the first friction factor and the second friction factor. ### Claim 18 (depends on 17) The one or more non-transitory machine-readable media of claim 17, further comprising program code to: based on a determination that the friction factor increases as a function of the number of centralizers in the wellbore, increase a value of drag per centralizer. ### Claim 19 An apparatus comprising: a processor; and a non-transitory machine-readable medium having program code executable by the processor to cause the apparatus to, determine a first value of at least one oppositional force for a drillstring at a first depth in a wellbore, wherein the at least one oppositional force includes a centralizer friction force based on the presence of one or more centralizers positioned within the wellbore at the first depth; determine a first value of hook load for the drillstring at the first depth in the wellbore based on the first value of the at least one oppositional force at the first depth; determine a second value of the at least one oppositional force for the drillstring at a second depth in the wellbore, wherein the at least one oppositional force includes a centralizer friction force based on the presence of one or more centralizers positioned within the wellbore at the second depth; determine a second value of hook load for the drillstring at the second depth in the wellbore based on the second value of the at least one oppositional force at the second depth; determine a first calibrated drillstring weight based on a difference between the first value of hook load and the second value of hook load; determine a friction factor based on the first calibrated drillstring weight; and control one or more drilling operations performed on the wellbore based at least in part on the friction factor. ### Claim 20 (depends on 19) The apparatus of claim 19, wherein the program code further comprises program code executable by the processor to cause the apparatus to: determine a third value of the at least one oppositional force for the drillstring at a third depth in the wellbore; determine a third value of hook load for the drillstring at the third depth in the wellbore based on the third value of the at least one oppositional force at the third depth; and determine a second calibrated drillstring weight based the first calibrated drillstring weight and on a difference between the second value of hook load and the third value of hook load.