TotalFinaElf’s Hubert Prouvost explained that fiber technology could be used both for data transmission and as a sensor. One technique allows for temperature monitoring along the whole length of a fiber. Another use of fiber is to monitor stress in platform anchor lines.
Some fiber applications rely on the diffusion of light by acoustic waves - discovered early in the last century by French physicist Léon Brillouin. Brillouin scattering can be used over distances as great as 30 km and gives metric resolution. While ordinary fiber can be used to measure temperature, strain measurements require sensors at intervals along the fiber.
Jacques Danquigny described TFE’s ‘Izaute’ passive seismic monitoring project. Here Weatherford’s ‘Optoplan’ technology is used to monitor the water/gas contact in a gas storage reservoir. The project was deemed very successful—and did not require any specific hardware or data processing software.
Nigel Legget from Schlumberger’s Sensa unit described how the DTS technique was used for inflow monitoring, well integrity, crossflow identification, etc. Sensa claims 230 oil and gas installations monitoring temperatures from 20°C up to 305°C. One BHP Billiton test was conducted in an ‘intelligent well’ to determin flowrate, water breakthrough, ESP monitoring; all of which was performed with one tool.
Some operators expressed the opinion that this technology was still immature and moreover very expensive—a position which was contested by the vendors. But the expense is deemed worthwhile in subsea completions and complex wells. One deployment revealed that an offshore well had drilled 2000 m too far!
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