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Riser Margin and Loss of BHP

The document discusses the calculation of Bottom Hole Pressure (BHP) loss if a riser is lost, detailing the necessary formulas and parameters such as seawater density, water depth, and air gap. It provides specific calculations showing that the BHP loss is 147.16 psi and outlines how to determine the required mud weight (MW) to maintain pressure after the riser loss. The final required MW is calculated to be 11.1 ppg after considering the riser margin.

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metador 786
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37 views7 pages

Riser Margin and Loss of BHP

The document discusses the calculation of Bottom Hole Pressure (BHP) loss if a riser is lost, detailing the necessary formulas and parameters such as seawater density, water depth, and air gap. It provides specific calculations showing that the BHP loss is 147.16 psi and outlines how to determine the required mud weight (MW) to maintain pressure after the riser loss. The final required MW is calculated to be 11.1 ppg after considering the riser margin.

Uploaded by

metador 786
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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BHP loss if riser is lost

Seawater MW Riser (Water depth + Air Gap)


density

Well TVD - Riser


BHP loss if riser is lost

8.6 ppg 10.2 Riser (Water depth + Air Gap)


ppg

Well TVD - Riser


BHP loss if riser is lost

Air Gap = 50 ft

Water depth = 1450 ft 8.6 ppg 10.2 1500 ft


ppg

When asked about how much BHP will drop if riser is lost, then
anything below BOP is not relevant.. The calculation will simply be
the differential pressure between the mud in the riser and the
hydrostatic from the water

BHP loss = P_hyd Riser – SW_hyd


BHP loss = (10.2 x 1500 x 0.052) – (8.6 x 1450 x 0.052) = 147,16 psi
Riser margin

Air Gap

Water depth 8.6 ppg 10.2 Riser (Water depth + Air Gap)
ppg

When calculating the riser margin (formula Well TVD


#26), you have to think about an added MW if
the riser is lost. This means that the SW_hyd
will be there + the P_hyd below, which has to
add up to the same as it was BEFORE the riser Well TVD - Riser
was lost.
Riser margin

Air Gap = 50 ft

Water depth = 1450 ft 8.6 ppg 10.2 Riser (Water depth + Air Gap)
ppg 1500 ft

Well TVD
5000 ft

Well depth below BOP = 3500 ft

Well TVD – Riser


3500 ft
Riser margin

Air Gap = 50 ft

Water depth = 1450 ft 8.6 ppg 10.2 Riser 1500 ft


ppg

Well TVD
5000 ft

Well depth below BOP = 3500 ft

Well TVD – Riser


3500 ft
Riser margin

Air Gap = 50 ft

Water depth = 1450 ft 8.6 ppg 10.2 Riser 1500 ft


ppg
SW_hyd = 1450 x 8.6 x 0.052 = 648.44 psi Riser_hyd = 1500 x 10.2 x 0.052 = 795.6 psi

Well TVD
5000 ft

Well depth below BOP = 3500 ft


Riser margin: ((795.6 – 648.44)/3500/0.052)) = 0,81 ppg Well TVD – Riser
MW needed = 10.2 + 0.81 = 11.01 = 11.1 ppg 3500 ft
(ALWAYS ROUND UP)

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