Schlumberger

Performance Report: Gulf of Mexico: Filtration Maintains Pace With Challenging Deepwater Displacement

Challenge: For the displacement of its deepwater well, the operator required filtered brine to its exact brine fluid specifications: NTU’s below 20, and solids less than 0.1% by volume coming out of well. Furthermore, adequate filtered brine volume must be maintained in the rig active pit to avoid stopping pumps during the displacement because of an inadequate supply of filtered fluid. The well included a riser volume of 2,592 bbl, hole volume of 1,172 bbl, and pit volume of 5,412 bbl for a total of 9,176 bbl. The rig would be displacing at a rate of 1,050 gal/min.

Solution: This ultra-deepwater project required two 1,500 sq/ft DE filter units, two filtration operators, and two filtration helpers.

Result: With a total of 9,127 bbl of completion fluid on location, the well was displaced from 12.5 lb/gal (1.50 s.g.) NOVAPLUS to 12.3 lb/gal (1.48 s.g.) CaBr2, utilizing the M-I SWACO proven displacement engineering guide lines on displacements. The key to the successful displacement was the seamless integration of:

  • Mechanical - Specialized Tools
  • Chemical - Displacement spacers designed by WP Tech Service Lab
  • Hydraulics - Flow regime designed using VIRTUAL COMPLETION FLUIDS (VCF) simulation software

A total of 10,950 bbl of 12.3 lb/gal (1.48 s.g.) CaBr2 brine was filtered in four filter cycles over 11 hrs. The rig pumped brine non-stop for 11.5 hrs and during the displacement from mud to brine, the rig pumped 20 bpm. At the onset, the well maximum NTU was 85 with 0.1% solids, and after filtration - NTU of 4, with solids 0%, and in pit NTU of 6. Using two filtration units to continually filter brine fluid, M-I SWACO Filtration exceeded the rig requirements for filtered fluid.

With workstring on bottom, the well was displaced to brine at 20 bpm for a total of 9,176 bbl. During the displacement, two 1500 sq/ ft DE units filtered 3,840 bbl at a rate of 10 bpm each for a total of 20 bpm. A total of 1,440 bbl of brine were reversed out at 8 bpm, maximum NTU out of well 71 and after filtration NTU of 4, in pit NTU of 6 and 0% solids. While reversing out, one filtration unit was shut down, cleaned, and pre-coated before being brought back on line, after which the second unit was shut down, cleaned, pre-coated and returned to service. While reverse circulating at 8 bpm, one filtration unit was able to filter at the same rate that the rig was pumping, allowing the cycling of each unit to be ready when it was time for the rig to pump down the drill pipe and up the annulus at a rate of 20 bpm. The BOP stack was jetted and the riser boosted at a rate of 11 bpm. After circulating 2,700 bbl NTU out of the well, NTU after cartridges 4, and in the pit NTU was 6. Circulation continued for an additional 2,640 bbl at 11 bpm. Once the rig discontinued circulating, an additional 330 bbl of brine was filtered to top off pits with a total of 10,950 bbl filtered in 11.5 hrs with no down time. By the time M-I SWACO Filtration was released from the rig, a total of 30,150 bbl had been filtered trouble-free.


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“Wellbore Productivity Filtration has met and exceeded the filtering challenges for today’s deepwater brine volumes. In 24 hours, we displaced 12.5 lb/gal SBM to 12.3 lb/gal calcium bromide and filtered a total of 10,950 bbl of brine in four (4) filtration cycles with no interruption of rig pumping to clean filtered brine.”
Mitch Broach
Completion Fluids Business Development Manager

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