Paul E. Sanders

Large-diameter waveguide Bragg grating components and their application in downhole oil and gas sensing

A new class of Bragg grating components based on large diameter cylindrical waveguides has been commercially released. Unique properties of the waveguide including grating fabrication, low loss splicing to optical fibers, and specialized machining for optimization in sensor applications are reported. The waveguide structure enables packaging of Bragg gratings that overcomes attachment, mechanical creep, and hermeticity problems commonly associated with fiber Bragg gratings. This enables exceptionally robust Bragg grating sensor transducers well suited for the high temperature, corrosive downhole environment of oil and gas. Sensor transducers have been demonstrated showing no measurable drift or error after over 4-year aging tests at 150°C. More than 50 pressure/temperature installations have been successfully completed and are operational, delivering real-time data cumulatively over 500,000 operation hours. These systems integrate a range of support components specific to in-well oil and gas applications, such as downhole cables, interconnects, and platform instruments. This optical sensing platform, coupled with other optical techniques, has been extended beyond optical pressure/temperature measurements to distributed temperature measurements, multiphase flow, and in-well seismic sensing. These systems have been successfully deployed in multi-zonal, multi-parameter system architectures. This sensing technology is integrated with in-well controls, data acquisition and interpretation, and reservoir modeling. This systems approach is required to close the value loop of intelligent completions in oil and gas production.