Procedure for Setting Short Plugs

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Where small amounts of cement are used, eg., when setting a plug across a window cut in casing, of maximum length 50 ft, the plug can be set by the “running plug” method as detailed below:

1. Run in with stinger to required depth. Ensure that the circulating head is only one metre above the drillfloor when the drillpipe is spaced out for pumping.

  • Note:   The stinger should have side jets and should be at least 100 ft longer than the planned cement plug. Use 3.1/2in or smaller tubing in holes with a diameter of 12.1/4in or less. The smaller the diameter of the stinger the less will be the disturbance to the cement when pulling out of the plug.

2. Circulate a minimum of 150 % of the drillpipe/stinger contents prior to setting the cement plug. The mud must have a constant gradient prior to commencement of the job.

3. Pump preflush

4. Mix and Pump cement.

  • Note:   The slurry for cement plugs should be batch mixed. When this is not possible, the slurry must be dumped until a  consistent gradient is achieved. Density shall be checked using a pressurised mud balance.

5. Pump postflush, to balance the preflush pumped ahead of the slurry.

6. Chase with mud. As soon as the cement is +/- 50 ft in the annulus, RAISE drillpipe slowly to the maximum distance possible above the rotary table, while continuing to displace to the balance point.

7. Pull back to the required top of cement. If the excess cement is to be circulated out conventionally, Pull back to a position 10-15 ft higher than the required top of cement to minimise disturbance caused by the jetting action of the stinger.

8. Circulate out excess cement immediately after placing the plug. The top of good cement should be known with fair accuracy after the job. Use reverse circulation  except in the circumstances detailed below.

Conventional circulation shall be used when:

  • formation strength is known to be sufficient to support the increased back pressure.
  • there is no chance that the back pressure will cause differential sticking.

9. If the plug has to be tagged after the cement has hardened, Pull back one more stand and keep moving the stinger while waiting on cement (WOC). Never stab the cement stinger back into the plug when the displacement is finished as this may cause plugging of the stinger.

10. Set the next plug or POOH.

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