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26” Section - Cementing – Checklist.

Preparation Checklist

  • Ensure the Cement Program has been received. Calculations of cement quantities and volumes should be checked by both the Drilling Supervisor and the cementing operator. Compare job duration with thickening and compressive strength development times. Check design temperature.

  • Discuss with rig team the contingency plans for failure of float equipment, losses and packing off during the cementation.
  • Check that casing is secured before starting the cement job.
  • The slurries have thixotropic properties (high YPs) so it is important to keep pumping, even if only at a low rate. Once pumping has stopped it will be difficult to get the slurries to move again.
  • Cement stinger will need to be tied-down to prevent pump-out during the cement job.
  • The cement mix fluids for the lead and tail slurries will be prepared in two separate batch mixers.
    • This must be done before the casing has reached bottom. It is better to dump the mix water than to have the rig waiting for mix water to be prepared.

  • The annular excess volumes will be 100% for the lead cement slurry and 25% for the tail cement slurry based on experience of the previous cemented surface casings.

  • The spacer is to be prepared in the rig slug pit and final surfactant added while circulating at TD.
  • Both cement slurries will be mixed on the fly and pumped at 3 bpm (plug flow displacement). This rate is sufficient to allow the cellar pump to transfer the returns and prevent the cellar form overflowing.
  • If the lead cement does not reach surface (losses), or the top of the cement drops in the annulus, a top up job will be performed using a fast setting 1.9 sg slurry, accessing the annulus with a spaghetti pipe. This job should be done off the critical path.
    • Ensure spaghetti pipe is readily available for performing a cement top up job.
    • Ensure a cement program for a top up job is available on the rig.

  • The job is designed so that the maximum ECD will not exceed 1.64 sg at the 20" casing shoe and 1.52 sg at the 30" casing shoe. The effective casing weight will be positive under static and dynamic conditions with 1.05 sg mud in the 20" Casing x Drill Pipe annulus.

  • If losses are seen during the drilling the section, thixotropic cement can be considered.
  • Check the hook up of the transfer pump from the cellar to the waste disposal tank to take returns during cementing.  Run a clean-up line to the rig floor in the event pumping is stopped and the slurry needs to be cleaned out of the surface lines.

Sequence of Operations

  • Pump string volume to ensure it is not plugged up.
  • Stab-in.
  • Fill 30" X 5" annulus, if necessary, and monitor fluid level to ensure inner string is not leaking.
  • Circulate at least 1.5 x annular volume while monitoring returns to ensure hole is clean and is not packing off.
  • Hold a Pre-Job Safety Meeting whilst circulating.  Personnel must be made aware of their responsibilities, understand the job sequence, pressure limits, communication signals for opening/closing valves, etc.
  • Prepare 6 m3 of spacer while filling the cement unit displacement tanks with Technical Water.
  • Fill the cement lines with Technical Water (1 m3) and pressure test lines to 3000 psi for 10 min.
    • During winter months use saturated brine instead of technical water

  • Bleed off pressure and pump the spacer at 3 bpm

  • Mix and pump 1.5 sg lead slurry at 3 bpm.  Take representative cement slurry samples, label and place in oven or waterbath set at bottom hole temperature.
  • Once the lead cement slurry returns reach 1.45 sg, switch over to the tail slurry. This will ensure that by the time the tail slurry has been displaced, the returning cement slurry will have a density of 1.50 sg, without pumping excessive volume of lead cement slurry.
  • Mix and pump the 2.0 sg tail slurry at 2 bpm. Take representative cement slurry samples, label and place in oven or waterbath set at bottom hole temperature.
  • Add sugar in cellar on noticing cement. Use vacuum truck to remove returns from cellar.
  • There should be minimal pressure throughout the displacement of the cement, if pressure starts to rise suddenly, shut down pumping and investigate. If the problem is due to a restriction in the annulus, attempt to pump the tail at reduced rate. If the job can’t be completed, a top job will be performed later.
    • Note: Max pump pressure should not exceed 300 psi throughout the job. The casing collapse pressure is 520 psi.
    • Mud Engineer should be near cellar area during the cement job to record return slurry weight and also monitor 20” casing for stinger seal leak. Make sure sugar bags are near cellar (require at least 6 large bags of sugar).

  • Displace cement in the inner string with technical water or saturated brine (winter months), using cementing unit. Leave +/- 15 m inside DP.

  • Purge the cement line to the cement unit displacement tank and monitor returns. If the float does not hold pump back the returned volume and shut in the cement line and monitor pressure. When the cement start to set the pressure should drop off.
  • If no returns, sting out and observe for 10 min the level in the casing to confirm float is holding. If the float doesn’t hold, sting back in, with cement line closed at surface and wait for another +/-10 minutes.
  • Flush 1.5x DP volume and POOH cement stinger.
  • Install the Wear Bushing.

Notes:  If losses during cementing

  • If losses occur after cement has reached surface, complete the job and a top job will be done later on.

  • If total losses occur during the cement job, reduce the mixing and flow rate of cement and check for improvement.
  • If the situation improves, complete the cement job as planned.
  • If cement has not reached surface, a top job to fill up the annulus will be performed later.