Lessons Learned from the First Application of Fiber-Optic Monitoring and Cemented Coiled Tubing-Enabled Multistage Fracturing Sleeves for Real-Time Monitoring of Stimulation Treatments and Post-Frac Production
Authors: Castro Luis , Lee Erik , Elliott Christopher , Howard Jesse 
Published: October 2016

Unconventional reservoirs require innovative completion techniques and technology to become more economical. When breaking into relatively new rock – or even due to unconventional reservoirs' intrinsic heterogeneity – multiple challenges can arise during the completion phase that can exceed authorized expenditures. Consequently, understanding the reservoir and identifying the zones with higher production potential is highly desirable. During the unconventional revolution of the last decade, with triple-digit oil prices, the industry could afford a few mistakes. In the current market environment, the story has significantly changed.

This paper focuses on an operational review and lessons learned during the deployment and fracturing of a unique coiled tubing (CT) frac sleeve system along with a fiber-optic monitoring system. The installation, conceived to provide the operator with a better understanding of the reservoir for future development, used an industry-first combination of permanent fiber-optic sensing cable clamped to the outside of the casing string with CT frac sleeves in a cemented application. This paper also looks at the fracturing job as seen through the fiber-optic monitoring to provide reservoir understanding during the fracture stimulation. It also includes a short summary on some of the post-frac production surveillance as an additional layer of unique information for future field expansion.

Unlike traditional completion methods, CT-enabled frac sleeves do not involve dropping balls or setting composite plugs to isolate stages. The technique uses frac sleeves activated with a CT bottomhole assembly to save time and fluid between stages as well as to provide distinct contingency options. The sleeves and fiber-optic cable can be cemented in place as part of the completion if desired and have a full-bore internal diameter that does not require post-treatment millout operations, further reducing overall completion time and time to production.

The operator used this method due to its targeted nature, efficiency, and fluid savings as well as the ability to use the data obtained from the fiber-optic installation to change the frac design on the fly. CT frac sleeves provide several benefits for this application including simple compatibility with deployment of the fiber-optic system, fracture treatment flexibility, and excellent fracture control. Multicluster fracturing methods (such as "plug-and-perf") can be costly due to the need to identify the fiber-optic cable and then orient the guns to prevent firing through the cable. On the other hand, this system removes risk and cost as the basic geometry of the CT frac sleeve and clamp protects the cable from damage. A single entry point during the frac job promotes increased fluid velocity, enabling a more aggressive sand ramp and a reduction in required hydraulic horsepower. Similarly, the single entry point ensures that a fracture is generated at each port, as opposed to the possibility of leaving some clusters untreated.

The paper contributes a novel insight to the stimulation and production monitoring industry as it describes the first application of CT frac sleevs used in conjunction with fiber-optic cable. It also provides relevant information on a cost-effective alternative to orienting guns to eliminate irreversible damage to the fiber-optic cable as well as a solution for operators to better understand their fields.