Volumtric Stripping

5.6.1 Example of Volumetric Stripping

The options available if an influx is swabbed or if the well starts flowing during a trip are as follows:-

  1. If well is not flowing, trip back to bottom keeping a careful check on returns. Then circulate influx out of hole.
  2. If well is flowing and is shut in and the gas is percolating with the bit a long way off bottom and tight hole conditions have been experienced, then consider doing a volumetric bleed.
  3. If well is flowing and is shut in and the gas is percolating with the bit a long way off bottom and tight hole conditions have been experienced, then consider bullheading.
  4. If well is flowing and is shut in and the gas is percolating and no problems are anticipated in stripping back to bottom, then consider volumetric stripping to get bit to bottom. Circulate influx out using first circulation of Driller's Method.

Note: A swabbed kick well can be most effectively killed with bit on bottom. So every effort must be made to get bit safely back on bottom.

SECTION 5 : METHODS OF WELL CONTROL

5.6.2 Well details

Figure 5.13

Jos)

15 bbls Figure 5.14

J60)jv

Bit size

8 1/2"

TVD

12,000'

TVD shoe

9,000'

Bit Depth =

11,000'

DP Cap

0.02776 bbl/ft

DP Disp =

0.0075 bbl/ft

DP/OH cap

0.0459 bbl/ft

Mud wt

12.0 ppg

Pit Gain

15.0 bbls

Influx Grad

0.12 psi/ft

Bit depth at original shut in = 11,000'

Shut in pressures and influx size with bit on bottom.

24.5 bbls

SECTION 5 : METHODS OF WELL CONTROL

  1. 6.3 Shut in procedure for a swabbed kick while tripping Fast shut-in
  2. Stab safety valve (kelly cock).
  3. Close safety valve.
  4. Open HCR fail safe valves.
  5. Close annular.
  6. Read casing pressure and if possible read drill pipe pressure.
  7. Stab inside BOP (Gray valve).
  8. Open safety valve.
  9. Do stripping calculations, prepare stripping sheet.
  10. Reduce annular pressure and commence stripping drill pipe.

Note: The above procedure (steps 1 through 5) assumes there is no float or non-return valve in the drill string.

5.6.4 For calculating safety margins and working margins use the universal volumetric well control equation below:-

choke

rann rs rw

Initial SICP

100 psi + *Increase in casing pressure with influx around drill collars * AP.csg = Mud grad - Influx grad x (H2 - Hi)

Working margin (Recommended working margin = 50 - 100 psi)

15 15

214'

choke

0.07 108 psi

100 + (0.624 - 0.12) x (514 - 214) 100 + 0.504 x 300 251 psi

50 psi

0.0292

514'

SECTION 5 : METHODS OF WELL CONTROL

Theoretical bleed off in bbl/ft while stripping = DP displacement + DP cap

  • 0.01776 + 0.0075 = 0.02526 bbl/ft
  • Ann Cap \

Mud grad /

Note: If the gas is not migrating while stripping, only theoretical bleed off will be seen in strip tank.

If gas is migrating then any excess bleed off is due to migration. When excess bleed off is ± 2.3 bbls, then build in another 50 psi working pressure. Refer to Volumetric Stripping chart (Fig. 5.15).

Figure 5.15

Step 1

Step 2

Step 3

Step 4

Step 1

Step 2

Step 3

Step 4

P° choke

Average length = 94' No. Stands

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Responses

  • MACKENZIE
    What is stripping with volumetric control?
    8 years ago

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