Objective
The objective of this project is to demonstrate the technical feasibility of a downhole permanent optical pressure gauge to work at high temperatures (range 20° to 200°C). This gauge is based on the EAP/GIP patent and the double detection pressure and temperature gauge developed in the framework of the PLATINE project. Geoservices had been contracted by the consortium in order to complete this project, bringing it to commercial status.
The absence of downhole electronics should allow this pressure monitoring system to respond with similar accuracy, better resolution and longer term stabilily when compared to a standard electronic pressure gauge but at elevated temperatures in excess of 200°C.
Present electrical systems with downhole electronics are subject to rapid wear and the electrical lines are subject to failures due to lack of insulation or short circuits. These failures will be eliminated by the use of a fiber optic transmission medium.
Phase 1 completed.
Phase 2 nearly completed - pre-serie sensors integration completed (2 sensors)- surface system manufacturing completed (1surface system)
The installation of this optical pressure sensor may be compared to that of a classic electronic gauge. The sensor is installed in the annulus on the production tubing, beneath the packer. The fiber optic cable linking the downhole sensor to the surface system is clamped to the production tubing from the bottom of the wellbore to the wellhead. The fibre optic cable must then pass through an optical high temperature high pressure wellhead feedthrough before connection with the surface detection system.
The transmission system used (white light interferometry) eliminates any factors influencing signal transmission between the downhole sensor and the surface acquisition system. Only one optical fiber is necessary to link the sensor to the surface measurement system. Encoding principle is based on the modulation frequency of a broadband source illuminating an interferometer in which the optical path difference is a function of the physical parameter to measure.
The sensor consists oftwo interferometers connected in series, one responding to temperature variations and the other to pressure variations. Light supplied by the surface system along the fiber optic cable is coded as a function of pressure and temperature by the downhole interferometer system. The double-modulated signal is transmitted back along the optical fiber to the surface where data relating to temperature and pressure may be separated and converted hy the surface module.
Knowledge of real-time, continuous pressure data allows wellbore behaviour to be determined and production to be optimised. Currently, for high temperature wells, only data at any one point in time is available.
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DEM - Demonstration contractsCoordinator
93151 Le Blanc-Mesnil
France