The optical seismic system was deployed in a well at the Izaute Gas Storage in southwestern France for TotalFinaElf. The installation represents the validation of the high performance, fiber Bragg grating-based multi-channel in-well seismic system developed by Weatherford and its specialist subsidiary, Optoplan. The design qualification and installation project, led by Optoplan, was supported by the Norwegian Demo 2000 Program and the project's oil company participants: TotalFinaElf, Statoil, Norsk Hydro and BP.
"Cooperation with the oil companies has been crucial in developing this technology. The Demo 2000 program gives a unique opportunity to establish close technical collaboration within the oil companies and eases the identification of potential well candidates for essential field trials," says Hilde Nakstad, project manager for the field trial.
The multi-station optical seismic system was tubing conveyed with the accelerometers optimally coupled to the casing. Five 3-C seismic stations were used for a walkaway Vertical Seismic Profile (VSP) survey, with repeat VSP surveys planned for time-lapse imaging. A sixth 3-C station, installed at the reservoir level, will be used for continuous recording of micro-seismic events.
"TotalFinaElf is very satisfied with the way Weatherford has combined advanced sensor technology with standard completion components and configurations. The seismic sensors were installed with minimum of extra equipment and precautions and we were very happy to host this field trial. The data from the fiber optic sensors will be processed using standard techniques -- our immediate reaction is that the data from the tubing conveyed fiber optic seismic sensor is easily comparable with the data recorded with conventional geophones," says Jacques Blanco, borehole seismic advisor from TotalFinaElf in Pau.
The Weatherford in-well optical seismic system has been specifically designed to meet the requirements for high performance multi-component seismic imaging, including high sensitivity, broadband response, high resolution and wide dynamic range. To meet the challenge of permanently operating in the in-well environment, the system uniquely combines these sensor characteristics with high temperature/pressure capability and deployment simplicity. The system employs cutting edge fiber optic multiplexing techniques for single-cable operation and miniature fiber optic seismic accelerometers for deployment in tight borehole areas. Furthermore, the all-fiber in well network design requires no downhole electronics.
"This installation represents the successful achievement of a four-year program to develop a unique sensor system for the seismic industry and to demonstrate that fiber optic seismic sensors are a superior alternative to conventional electronic devices," says Tad Bostick, VP Business Development-Intelligent Completion Technologies. Bostick added that fiber optic seismic sensors can be combined with Weatherford's other fiber optic sensors, including pressure, temperature, multi-phase flow and distributed temperature sensing to offer the most comprehensive and reliable in-well reservoir imaging and monitoring capability available today.
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