Quantcast
Viewing all articles
Browse latest Browse all 499

Riser Margin – One of Important Concepts For Deep Water Drilling

Riser margin in the mud weight increase below mud line to compensate bottom hole pressure in case of an accident disconnect or a failure marine riser close to the BOP stack at sea bed.

The riser margin is described by a following equation:

Image may be NSFW.
Clik here to view.
Riser Margin - equation

Where;

ρrm is riser margin, ppg

ρdf is drilling fluid density equivalent to formation pressure, ppg

ρsw is sea water density, ppg

L is riser length from sub sea BOP to rig floor, ft

D is true vertical depth of the well, ft

DW is water depth, ft

Note: When you consider adding the riser margin, you need to make sure that formation strength is sufficient. Additionally, you must not add trip margin and riser margin to the system because it is way over safety factor. If trip margin is higher than the riser margin, you must use the trip margin.

Example: Determine riser margin for this case.

Image may be NSFW.
Clik here to view.
Riser Margin

Drilling fluid weight equivalent to formation pressure = 9.2 ppg.

Sea water weight = 8.6 ppg

Length of riser to the rig = 8000 ft

Well TVD = 13,000 ft

Water depth = 8,000 ft

Image may be NSFW.
Clik here to view.
Riser Margin - equation 2

 

ρrm = 1.2 ppg

Riser margin for this case is 1.2 ppg.

Reference book: Image may be NSFW.
Clik here to view.
Well Control Books


Viewing all articles
Browse latest Browse all 499

Trending Articles



<script src="https://jsc.adskeeper.com/r/s/rssing.com.1596347.js" async> </script>