Record seven-WAB completion enables multistage stimulation in ultra-deepwater Brazilian pre-salt formation

Background

Brazilian pre-salt developments continue to push the boundaries of completion design, driven by ultra-deepwater conditions, extended measured depths, high differential pressures, and the need for reliable, cementless zonal isolation.

In this context, one of our clients required a completion architecture capable of supporting selective multi-stage stimulation, while ensuring long-term well integrity across multiple producing, intermediate, and non-productive intervals.

The well represented a particularly demanding scenario, requiring precise compartmentalization of the openhole section combined with a robust stimulation strategy.  The challenge was to integrate a large number of annular barriers with sliding sleeve valves, maintaining operational simplicity and minimizing risk in one of the most demanding offshore environments in the world.

Solution

The 812 Welltec® Annular Barrier (WAB®) was selected for its ability to:

• Provide high-integrity, bidirectional annular isolation in open hole.
• Withstand high differential pressures during stimulation operations.
• Maintain isolation performance under complex thermal and mechanical loading.
• Eliminate cement, reducing uncertainty and operational exposure.
  

Furthermore, the completion incorporated multiple Welltec® Flow Valve (WFV) units in 512 and 758 sizes to enable controlled multi-stage stimulation.

Well architecture and installation

Despite the complexity associated with installing seven metal expandable packers and multiple sliding sleeves in a single completion string, the installation was completed in a single trip, significantly reducing rig time and operational exposure.

• All 812 WABs were expanded and set at their planned depths.
• Annular isolation was achieved and maintained across all zones.
• 512WFV and 758WFV sliding sleeves were reliably actuated to conduct the stimulation sequence.

The seven, 812WABs were strategically positioned to segment the well into multiple functional zones (see schematic):

• Upper producing zone – isolated and stimulated selectively.
• Intermediate zones – isolated to prevent crossflow during high-pressure stimulation.
• Lower producing zone – independently accessed for stimulation.
• Dead zone isolation – preventing undesired fluid communication.

Stimulation strategy

Once annular isolation was established by the 812WABs, stimulation operations were conducted using a combination of 512- and 758-WFV sliding sleeves.

These completion technologies enabled precise sequencing of stimulation stages, allowing each zone to be treated individually while maintaining pressure integrity in adjacent intervals. 

The integration of expandable annular barriers with sliding sleeves ensured that high stimulation pressures were applied only to the intended zone, without compromising annular isolation or overall, well integrity.

Achievements

• Welltec record deployment in Brazilian Pre-Salt: Seven 812WABs installed in a single Brazilian pre-salt well.
• Integrated stimulation solution: Successful multi-stage stimulation utilizing 512- and 758-size configurations.
• Enhanced well integrity: Reliable annular isolation during high-pressure stimulation operations.
• Operational efficiency: Single-run completion for reduced complexity, rig time, and NPT.
• Risk reduction: Cementless isolation, minimized uncertainty, and improved operational confidence.

This 2025 case history represents a significant milestone in the evolution of openhole, cementless completion architectures for Brazilian pre-salt developments, demonstrating that complex, multi-zone stimulation programs can be executed safely and efficiently while maintaining the highest standards of well integrity.