Performance Report: RAPID SWEEP Cleans Problematic Hole, Cuts Costs in Casing Drilling Program

Southern Iraq

Challenge: Historically, the Damman Formation has been regarded as the most technically challenging in the South Rumaila field. Over the years, various lost circulation pills, techniques, and BHAs have been employed to reduce time and drilling costs. The operator recently decided to forgo LCM and cement pills and drill the Damman with water and a casing drilling assembly. Owing to the underlying thief zone, the Ghar Sand immediately overlying the Damman tends to become destabilized once the protection of drilling fluid is removed. Accordingly, the operator was forced to perform frequent HV sweeps during the casing drilling operation. Pills up to 10m3 (63-bbl) were pumped every 5 min., thus adding to the costs associated with higher water consumption, water hauling, and chemical consumption.

Solution: As an alternative to the frequent and high-volume HV sweeps, ALPINE SPECIALTY CHEMICALS suggested the operator use its RAPID SWEEP POLYMER stick technology. Several pre-planning meetings and discussions were held to outline the potential benefits and advantages, including:

  • Reducing the high water consumption required by conventional HV sweeps
  • Cutting chemical costs compared to the large volume conventional HV sweeps. Rapid Sweep also would allow for a pill tank for additional fluid storage
  • The technology would provide lubricity for torque control and anti-accretion aid for the bit / BHA
  • Cost effective means to maintain proper hole cleaning as predicted by M-I SWACO’s Virtural Hydraulics.

Result: RAPID SWEEP helped alleviate solids build up around the bit, BHA, and 13 3/8-in. casing drilling string in situations with and without fluid returns. The polymer sticks had no adverse effect on fluid properties or BHA. More importantly, RAPID SWEEP:

  • Cut costs 78% as compared to conventional HV sweeps
  • Provided more sweep action as observed on shaker beds, up to 80% coverage compared to 20% coverage with conventional sweeps
  • Delivered intermittent ROP increases, suggesting consistent dosage will yield better results
Eliminated all plugging of bit or BHA concerns. The operator plans to continue and increase the use of RAPID SWEEP on each connection in its multi-rig program, with both conventional and casing drilling BHA’s.

The Details

While RAPID SWEEP was used on a trial basis for this initial casing drilling program, the field trial also was intended to evaluate the potential drilling efficiency increases that could be achieved in future conventional BHAs as well. Trial results confirmed the capacity of RAPID SWEEP technology to provide economical, efficient hole cleaning, lubricity, and anti-accretion benefits and can help enhance drilling performance.

Despite an acceptable YP, the conventional pill (left) covered less surface area on the shaker while drilling with 2,000 liter/min (with approximately 70% fluid returns at surface).

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