1 Petroleum Engineering 406 Floating Drilling Lesson 11b Motion Compensation.

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Petroleum Engineering 406 Floating Drilling

Lesson 11b Motion Compensation

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Lesson 6B - Motion Compensation

Tensioners Heave Compensators Passive Motion Compensation Active and Semiactive Systems

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Motion Compensator

Principles ofOperation

Purpose:

Keep bit on bottom

with low bit weight change

Air pressure can support entire weight of drillstring. e.g. 200,000 - 40,000 = 160,000lbf. Reduce air press.

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Heave Compensation for Bit

We can compensate at Crown Block

or at Travelling Block

Example: Keep bit weight within 30% of average value.Hook load = 200,000 lbf. Avg. bit wt. = 40,000 lbf

Bit Weight must be kept within 0.3 * 40k = 12k lbf.

i.e. keep Hook load within 12/200 * 100% = 6% !!

How is that possible? Larger air tanks!

Rucker Heave Compensator

Dual Pistons- on the travelling block

Large air cylinders below deck

Flexible hoses

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Figure 7-9 Vetco dual piston Heave Compensator

L.P. hydraulic fluid throttled for damping

Piston balancing may be problem

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Western Gear Heave Compensator

Figure 7-10

Split travelling block

Hydraulically operated pistons can be locked in any position with remotely operated valves.

Air operated units must be mechanically locked in position because of compressible fluid in cylinders.

Single Piston Rod

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Crown Block Heave Compensator

AIR STORAGE