Formation-Testing Buffer Tube
From Complexity to Simplicity: The Success Story of a Redesigned Pressure Temperature Buffer Tube with Additive Manufacturing
The buffer tube is an essential component of the wireline formation testing tool, designed to sample downhole formation fluid after a well is drilled. It creates a buffer volume between the tool’s internal oil and the formation fluid being sampled to avoid sensor contamination retaining the hydraulic connection.
Existing Design
The original buffer tube subassembly was composed of seven parts, featuring several weld joints and dissimilar metals. This design was marked by limited rigidity and complex manufacturing and assembly processes, leading to multiple failure modes and a poor reliability record. The brazed joint, in particular, caused downhole leakages. Additionally, we needed to address design constraints to fit a smaller-diameter formation testing tool.
Validated Technology
Additive Manufacturing Engineering completely redesigned the buffer tube to enhance reliability and consolidate parts. The new design is printed as a single component using just one metal, eliminating the need for joints. Fluid flow channels are fully enclosed within the part, removing the necessity for brazing connection points. This redesign has eradicated all previous failure modes. Remarkably, the development process took just one month. Since its launch in 2016, the new buffer tube has accumulated thousands of operating hours with zero quality alerts.
Performance Opportunities
- Eliminate field failures improving design.
- Enable a compact design for smaller tools.
- Reduce lead and assembly time.
Challenges
- Design a module that could be a drop-in replacement.
- Combine 7 individual components into a one-piece component.
- Maintain the performance of the buffer tube with the new design.
- The fluid channels must be free of any powder prior to heat treatment.
Results
- Successful design and retrofit of the part has met all the functional requirements of the previous buffer tube.
- Successfully achieved a design where 7 parts were consolidated into 1.
- Reliability issues were completely addressed through the AM design.
Project
- Reliability Improvement: 100% reliability of AM design.
- Consolidation of Parts: 7 pieces to 1 piece design.
- Performance: Maintained functional performance.