Offshore Kalimantan presents some unique challenges in zonal isolation. Two of the problems include low fracture pressure and a shallow gas zone. To overcome these challenges, the operator had resorted to pumping three different slurry systems, each designed to overcome one specific problem. The three slurries were:

  1. Low-density, gas tight slurry.

  2. Low-density filler slurry.

  3. Neat slurry.

The three slurry systems caused logistic difficulties in transportation, storage on the rig, job execution, and job design. In designing and executing the job, a good understanding of the actual open-hole size was important. If the hole was actually smaller than predicted, the filler cement would be placed over the gas zone.

During the execution of the job, the same problem could occur if too much filler cement was pumped. If this happened, gas migration was not controlled and a costly remedial job was pumped.

An extensive technical study resulted in the development of a single engineered-particle-size slurry system that simplified the job execution procedures, mitigated gas migration, and improved the quality of the overall cement job. Changes made to the physics of the cementing operations could also be pre-evaluated using an advanced u-tube simulator. Input of well and fluid parameters allowed analysis of the impact and optimization of slurry design prior to actual execution of the first new system trials. Impact of system reengineering effects on pump rates, wash/spacer volumes, surface/downhole pressures, and total job times could be predicted and design improvements made. Case histories are given on the first two successes using this new lightweight technology.

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