Transcript FloatDrill1
Petroleum Engineering 406 Floating Drilling Lesson 11a Motion Compensation 1 Lesson 6 - Motion Compensation Reentry Tensioners Heave Compensators Passive Motion Compensation Active and Semiactive Systems 2 Re-entry It is possible to re-enter a borehole without using guidelines! 1. Use land-based navigation equipment to get the vessel in the vicinity of the well or better still: Use GPS (Global Positioning System) 3 Re-entry, cont’d 2. Lower reentry string to a safe distance above the wellhead 3. Use position location equipment to complete the job: (i) Television camera (ii) Acoustic device - pinger or transponder (iii) ROV - Remote Operated Vehicle 4 Heave Compensation How do you maintain a constant tension on the marine riser - when the vessel heaves? How do you maintain a constant weight on the bit - when the vessel heaves? 5 Deadweight Riser Tensioning System Dead Weight (~constant tension) Dead Weight Slip Joint Marine Riser 6 Early design - OK up to 100,000 lbf. Attached to lower half of telescoping joint. Adds weight & is bulky... Pneumatic Riser Tensioning System 7 Pneumatic/Hydraulic Heave Compensation System Pneumatic/Hydraulic Tensioners: Take up much less room Facilitate changing the tension by changing the air pressure Can be used for the marine riser, the guidelines and the drill string 8 Pneumatic/Hydraulic Heave Compensation System Passive Systems are the most popular Require essentially no energy input Use an “air spring” with a variable spring constant Can keep the tension within ~ 15% or even less. 9 Pneumatic/Hydraulic Heave Compensation System Active Systems Require external energy through each load cycle Provides a highly consistent force But -- Has a high initial cost Has a high operating cost 10 1,500 psig WP 5 ft Typical Tensioner 20 ft 11 Lower sheaves are attached to the cylinder (and vessel), upper sheaves are attached to the piston rod