Development Of Realtime Monitoring System For Pressure Outside The Casing Based On The Fiber-Optic Sensing Technology

Monitoring the pressure outside casing is significant to develop oil-water wells. It can not only help us to know the production capacity and production performance of oil level underground, but also has significant meaning to the reserch of rest oil saturation level and adjusting development program, such as the wells net distribution. A reasonable pressure limitation of water injection will be worked out to reduce the speed of casing damage development and keep down the increasing number of casing damage well and decrease the losses by monitoring the pressure outside casing. In recent years, domestic and foreign scholars have been conducting research in monitoring the perssure underground, but recent achievements are limited to point mode and quasi-distributed, a request of fully distributed can not be fulfilled. And also the troditional sensors are not competent because of the complicated conditions underground and the request of monitoring layering pressure. So a kind of sensor and monitoring system which is competent to do the work is in need urgently.In accordance with the special circumstances of oil well and characteristics of Daqing oil field casing, this paper use Fibre Optical Sensors technology based on BOTDR (Brillouin Optical Tmie-domain Reflectometry) to monitor the pressure outside the casing, to realize the purpose of real-time monitoring. Main research work and achievements are as follows.First, based on BOTDR sensoring techniques, a sensor which is suitable for monitoring the pressure outside the casing is designed and developed based on spiral winding packaging structure with FRP; theory model of the sensor packaging structure is established to analysis and verify the hypersensitization characteristic; the sensor interface strain transfer is reserched based on BOTDR techniques, constitutive equation between brillouin frequency shift and monitoring pressure is obtained finally.Secondly, the sensoring characteristic experiment is achieved based on BOTDR sensoring techniques, the veracity of theory analysis and feasibility of sensoring plan are verified; A kind of temperature compensation method is proposed which is using ROTDR(Raman optical time-domain analysis) technique for the pressure monitoring. In addition, some theory analysis and experiments are carried out to validate the method.Finally, the design of pressure monitoring system plan is achieved. Completing the sets of optical fiber sensor networks monitoring the pressure outside the casing, comparing the results and collecting the data from the test wells, completing the real-time monitoring the pressure outside the casing.