VU Stripping

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  • 5/21/2018 VU Stripping

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    GJS:/VUstripping.ppt

    Combined Volumetric Stripping Method

    Pdp Pan Pdp2 Pan2

    H1H2

    Ps= (H2-H1) (rmud-rgas)

    Ps= safety margin for loss

    of HH when influx enters

    the DCs

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    Combined Volumetric Stripping Method

    Pdp Pan Pdp Pan2

    DV

    Pw= -------------- rmud

    Ann.vol OH/DC

    Pw= safety margin for loss

    of HH mud.

    Gas is expanding while

    rising up the well bore

    DV

    V is taken opposite DC,

    ie. Worst case

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    Combined Volumetric Stripping Method

    Pdp Pan

    Pchoke1= Pan+ Ps+ PwLet Pchoke increase to above value

    while stripping in stands dp.

    Alternatively : Bring annular pressure to above value byusing the rigpumps.

    Bleed of CE dp vol after each stand stripped

    into striptank

    When increase intriptank DV due to gas expansion

    increase Pchoke1by Pw(50 psi)= Pchoke2

    When increase intriptank DV due to gas expansion

    increase Pchoke2by Pw(50 psi)= Pchoke3

    Pchoke

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    Combined Volumetric Stripping Method

    Pchoke1

    Triptank

    Striptank

    Stripping in stand no 1

    Volume 1 CE drill pipe

    Volume increase due to expansion

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    GJS:/VUstripping.ppt

    Combined Volumetric Stripping Method

    Pchoke1

    Triptank

    Striptank

    After stripping in stand no 1

    CE vol stand dp is bled

    off to Srip Tank

    Volume 1 CE drill pipe

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    Combined Volumetric Stripping Method

    Pchoke1

    Triptank

    Striptank

    Stripping in stand no 2

    Volume 2nd CE drill pipe

    Volume increase due to expansion

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    Combined Volumetric Stripping Method

    Pchoke1

    Triptank

    Striptank

    After stripping in stand no 2

    CE vol stand dp is bled to ST

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    Combined Volumetric Stripping Method

    Pchoke1

    Triptank

    Striptank

    DV

    When vol-increase in Triptank is equal

    to DV make Pchoke2 = Pchoke1+50 psi

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    Combined Volumetric Stripping Method

    Pchoke1

    Assume worstcase scenario:

    - Influx remains as one slug

    -Loss of HH due to expansion

    across smallest annular cross-sectional

    area, in most cases this is OH/DC

    After string is stripped to bottom succesfully

    Pchoke has been increased by several Pw

    Extra Back pressure has been applied

    BHP>Po

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    Combined Volumetric Stripping Method

    Pchoke1 Use checklist as per EP 89-1500

    Rig up as per checklist

    Lubricate pipeRemove sharp tong dies

    Minimise annular closing pressure

    Fill up each stand

    Install grey valve, open kelly cock

    Bleed of CE dp vol from Trip to Striptank

    Monitor Triptank level increase for vol DVCalculate Pw

    Calculate Ps

    Ensure all returns go to triptank

    Avoid annular leakage

    Avoid surgepressures

    Use Range of accurate pressuregaugesRemove dp/csg protectors

    Do NOT confuse strip and triptank

    On BTM kill well using the Drillers Method

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    Combined Volumetric Stripping Method

    Pch

    Questions:

    What will happen with Pw and Ps when

    there is no pipe in the hole?

    Suggestions on action once bit is through

    the influx??

    How to operate if no stripping tank available?

    Can we strip irrespective of wellbore pressurewhen there is no pipe in the hole?

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    Combined Volumetric Stripping Method

    closeopening

    line

    remove plug to ventopening chamberduring stripping

    bar200

    N2 precharge 400 ps i

    ANNULAR

    Clos ing l ine to TR

    regulating valve

    ballvalve

    gauge

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    Combined Volumetric Stripping Method

    TIME STAND

    NO:

    an

    w

    chPP

    PP

    an= ......

    = ......

    = ......

    Level inTriptank

    D VRemarks

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    GJS:/VUstripping.ppt

    Combined Volumetric Stripping Method

    Pchoke1

    Triptank

    DV

    When vol-increase in Triptank is equal

    to DV make Pchoke2 = Pchoke1+50 psi

    ABOVE EXPECTED INCREASE DUE

    TO CE displacement of the dp

    WITHOUT STRIPTANK