Method and system for mitigating cable wear in a hoisting system

Patent metadata

Field	Value
Publication number	US-11639639-B2
Application number	US-201916972569-A
Country	US
Kind code	B2
Filing date	Jun 6, 2019
Priority date	Jun 6, 2018
Publication date	May 2, 2023
Grant date	May 2, 2023

Abstract

A method for mitigating the effects of cable wear in an active heave compensated hoisting system of an offshore vessel in a locked to bottom mode of operation is disclosed. The method comprises supporting an upper end of a string which is connected to a subsea well from a travelling block of the hoisting system, wherein the travelling block is suspended from a crown block via a cable. The method further comprises operating an active heave compensation system to control a drawworks of the hoisting system to pay in and out the cable to compensate for motion of the offshore vessel and maintain a target overpull in the string. The method further comprises adjusting a ballast system of the offshore vessel to vary the draft of the vessel, and controlling the drawworks in accordance with the variation in the draft of the vessel to cause a length of cable to slip through the hoisting system and maintain the target overpull in the string.

First claim

The invention claimed is:

1. A method for mitigating the effects of cable wear in an active heave compensated hoisting system of an offshore vessel in a locked to bottom mode of operation, the method comprising:
connecting an upper end of a string which is connected to a subsea well to a travelling block of the hoisting system, wherein the travelling block is suspended from a crown block via a cable;
applying a target overpull in the string;
operating an active heave compensation system to control a drawworks of the hoisting system to pay in and out the cable to compensate for motion of the offshore vessel and maintain the target overpull in the string;
adjusting a ballast system of the offshore vessel to vary the draft of the vessel while operating the heave compensation system to compensate for motion of the offshore vessel; and
controlling the drawworks in accordance with the variation in the draft of the vessel to cause a length of cable to slip through the hoisting system and maintain the target overpull in the string.

2. The method according to claim 1 , comprising adjusting the ballast to cause a length of cable to move through the hoisting system without disconnecting the string from the travelling block.

3. The method according to claim 1 , comprising determining a requirement to slip the cable through the heave compensated hoisting system prior to adjusting the ballast system.

4. The method according to claim 3 , comprising determining a condition of the cable and adjusting the ballast system of the vessel in accordance with the determined cable condition.

5. The method according to claim 4 , comprising determining the condition of the cable based on measured parameters including at least one of applied load, elongation, strain and physical inspection.

6. The method according to claim 4 , comprising determining the condition of the cable analytically including at least one of software tools, numerical analysis, modelling and computational simulation;
wherein the analytical determination includes using physical parameters including at least one of historic use, loading, cable travel, relative movement between the travelling block and the crown block, historic use of the heave compensation system, ton-miles utilization of the cable, and geometry of the hoisting system.

7. The method according to claim 6 , comprising determining a required adjustment of the ballast system in accordance with the predetermined length of cable to be slipped through the hoisting system.

8. The method according to claim 1 , comprising performing offshore operations associated with the subsea well prior to the vessel entering the locked to bottom mode.

9. The method according to claim 1 , comprising slipping the cable through the hoisting system prior to the vessel entering the locked to bottom mode to replenish the cable within the hoisting system.

10. The method according to claim 1 , comprising performing a slip-and-cut operation prior to the vessel entering the locked to bottom mode.

Assignees

• Maersk Drilling As
• Noble Drilling As

Inventors

• Holck Jesper
• Hansen Kristian E

Classifications

• B66D3/043

  Block and tackle system with variable number of cable parts · CPC title

• E21B19/09 Primary

  specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string · CPC title

• E21B19/008

  Winding units, specially adapted for drilling operations · CPC title

• E21B19/006

  including heave compensators · CPC title

• B66C23/53

  including counterweight or means to compensate for list, trim, or skew of the vessel or platform (counterweights or supports for balancing lifting couples B66C23/72; equipment to decrease unwanted vessel movements B63B39/00) · CPC title