North Sea operator saves rig time using a lightweight foamed cement blend
Using the CemFOAM™ foamed cementing equipment, data acquisition, and control system, the operator achieved the section objectives for each of the seven tophole foamed cementing operations. The job time for each conductor took between 1.5 and 5 h. All wells were drilled to total depth without any issues.
A Norwegian-based operator drilled three wells in the North Sea from a semisubmersible rig. A critical factor for the customer was cementing the 30-in × 36-in conductors in place with the top of cement at seabed. On previous conductor jobs, where a conventional slurry system was used, a top-up job was required each time. Rig-time efficiency drove the need to design a novel approach to overcome the challenge with a reduced equipment footprint.
SLB recommended the CemFOAM foamed cementing equipment, data acquisition, and control system. The base fluid was designed with the special lightweight blend at a slurry density of 1.45 sg.
The foamed cement process-control system was used during the job and automatically synchronized the total N2 and foaming pump rates with the base slurry rate from the cementing unit. Seven tophole foamed cementing completions took place, with a job time for each conductor taking between 1.5 to 5 h.
For job fluid volumes, 20 m3 of viscosified wash was pumped followed by 47 to 112.5 m3 of lightweight base slurry, including a cap slurry of 2 m3 continuously mixed and pumped at 1.45 sg. Following N2 injection, the average foamed slurry volume across the seven jobs was 76 m3 with an average foam quality of 19%. The average foamed slurry density was 1.15 sg. The foamed lead slurry was followed by 10.3 to 15.1 m3 of unfoamed lightweight slurry and 4.5 m3 of seawater for displacement.
The liquid phase of the slurry formula used a liquid extender, fluid loss control additive, dispersant, and foaming additive. All these products are judged environmentally sound. The specialized lightweight blend developed compressive strength after 9 h.
No backflow was observed and no top-up job was required. The casings were set without any issues. Based on these successful completions, the innovative combination of foamed cementing and a special lightweight cement blend, developed by SLB, has become the operator’s solution of choice for future projects.
