Seepage Loss Mitigation in Deepwater well in the Gulf of Mexico

Abstract                                                                                                                                  Share Your Thoughts

This case study outlines the successful application of a tailored lost circulation material (LCM) and wellbore strengthening (WBS) strategy to mitigate seepage losses encountered during drilling operations in the 14½" × 16½" hole section of a deepwater well in the Gulf of Mexico. Through a combination of fit-for-purpose bridging materials and optimized treatment design, the operator achieved effective loss control, enhanced formation integrity, and reduced non-productive time (NPT). 

1. Introduction 

Drilling in deepwater environments presents significant operational challenges, particularly in managing fluid losses through high-permeability formations or natural fractures. This case describes a scenario where seepage losses in the intermediate hole section threatened wellbore stability and casing integrity. The operator implemented a customized LCM solution combined with a WBS strategy, resulting in effective loss mitigation and improved drilling performance. 

2. Operational Background 

  • Location: Deepwater Gulf of Mexico 

  • Well Section: 14½" × 16½" intermediate hole section 

  • Drilling Fluid: Synthetic-based non-aqueous fluid (NAF) 

  • Mud Weight Range: 12.1 – 13.5 ppg 

  • Well Depth: Confidential, but representative of deepwater conditions (typically >5,000 ft below seafloor) 

The geological setting consisted of formations with variable permeability and suspected natural fracturing, posing a high risk for seepage losses during drilling and casing operations. 

3. Problem Identification 

During the intermediate section, the operator observed gradual but persistent seepage losses. Although not categorized as total losses, the volume of fluid loss was sufficient to: 

  • Increase mud costs 

  • Complicate Equivalent Circulating Density (ECD) management 

  • Threaten cement placement quality 

  • Potentially induce differential sticking 

Preliminary diagnostics indicated that the losses were likely due to natural fractures and high-permeability intervals, underscoring the need for a robust, formation-specific loss control treatment. 

4. Remedial Strategy 

The operator deployed a two-pronged approach consisting of an LCM treatment and a WBS blend to arrest fluid migration and strengthen the near-wellbore region. 

4.1 LCM Treatment 

A high-concentration pill of BDF™-974 was pumped at 18 ppb, targeting micro-fractures and pore throats. This agent is known for its sealing efficiency in fine loss zones. 

4.2 Wellbore Strengthening Blend 

A 20-ppb WBS blend was designed using: 

  • BARACARB® 600 and 1200: Sized calcium carbonate for mechanical bridging 

  • STEELSEAL® 1000: Resilient graphite-based material to enhance seal durability 

  • BAROFIBRE®: Cellulose fiber to reinforce filter cake and prevent re-initiation of losses 

The treatment objective was to plug the loss pathways, reinforce the wellbore wall, and increase the fracture gradient for subsequent operations. 

5. Results and Performance Metrics 

Following the treatment, the operation demonstrated substantial improvement: 

Performance Indicator                                                   Pre-Treatment                                                       Post-Treatment 

Seepage Loss Volume                                                       Moderate, continuous                                        Negligible 

Leak-Off Test (LOT)                                                             Baseline                                                                       1.6 ppg increase 

Cement Returns                                                                   NA                                                                                   Partial/Full Returns 

Rig Time Saved                                                                      N/A                                                                                 ~3 days 

Mud Cost Reduction                                                          N/A                                                                                  Significant 

The observed increase in LOT values confirmed enhanced fracture resistance, allowing for safer casing and cementing without the need for additional mitigation measures. 

 6. Lessons Learned 

  • Customized LCM Packages Are Essential: One-size-fits-all treatments are often inadequate in complex deepwater formations. Tailoring particle size distribution and material types to the formation characteristics greatly enhances treatment success. 

  • Synergy of LCM and WBS: A dual approach that combines pore-sealing with mechanical strengthening provides superior control over seepage and enhances wellbore resilience. 

  • Monitoring and Adjustment: Continuous real-time monitoring of loss rates, mud properties, and ECD was critical to identifying losses early and evaluating treatment success. 

  • LOT as a Benchmark: LOT results post-treatment are a valuable indicator of improved formation integrity and can inform mud weight and casing design in real-time. 

7. Conclusion 

The case demonstrates the successful application of engineered loss mitigation strategies in a technically demanding deepwater well. The customized blend of LCM and WBS additives effectively controlled seepage losses, enhanced formation integrity, and resulted in cost savings and improvements in operational efficiency. This case highlights the importance of proactive fluid loss control planning and provides a replicable model for addressing similar challenges in deepwater drilling environments.