Oil Extraction Technology Research Institute, China

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1 Advanced Materials Research Online: ISSN: , Vols , pp doi:1.48/ 13 Trans Tech Publications, Switzerland Research of optical fiber fluid flow monitoring system using flow-induced pipe vibration in the oil production Ying SHANG 1,,a,Xiao-hui LIU 1,,Chang WANG 1,,Bao-quan Sun 3,Gan LI 3, Wen-an ZHAO 1, Guo-yu Zhang 3,ing-sheng LV 1,,Wei-song ZHAO 1, 1 Key Laboratory of Optical Fiber Sensoring Technology of Shandong Province,China Laser Research Institute of Shandong Academy of Sciences,China 3 Oil Extraction Technology Research Institute, China a sy81167@163.com, Keywords: oil, fluid flow,fiber optic sensors, real-time monitoring, reservoir recovery,turbulent flow,pipe vibration, non-intrusively Abstract. In the oil field development and production, fluid flow is an extremely important parameter which determines the transmission characteristics of the oil production, real-time monitoring of fluid flow parameter provides a scientific basis for oil and gas optimization exploration and increase of reservoir recovery. A method for interrogating fiber optic sensors using flow-induced pipe vibration is proposed, then the fixed relationship between standard deviation of pipe wall s vibration induced by fully developed turbulence and mean flow rate is determined.the advantage of this method is applicable to small flow measurement with non-intrusively. Introduction In the oil field development and production, pressure, temperature and flow are important parameters of well. Real-time monitoring of those important parameters provides a scientific basis for oil and gas optimization exploration and increase of reservoir recovery. In the oil industry, because of complex character of fluid composition and various flow state and bad working condition, conventional electronic sensors can not work in the underground environment such as high temperature, high pressure, corrosion and electrical interference and so on[1,]. New kind of the optical fiber monitoring system of fluid flow using flow-induced pipe vibration is proposed, By optimizing the design flow sensor,a turbulent flow device is placed in front of the sensor unit to enhance turbulence intensity, then a flow measurement has completed,the system has extensive application prospects in the oil field development and production because of high sensitivity, high accuracy and high stability. Measure principle of the system Principle of optical phase modulation. Optical phase depends on the three characteristics of optical waveguide when light transmits in the fiber: the total physical length, refractive index and lateral dimensions of optical waveguide. Waveguide is supposed to be monochromatic when light transmits in optical fiber, and its wavelength in the air is λ. Optical waveguide refractive index distribution is supposed to be constant with the external changes, and the disturbance is applied to the fiber, the optical phase sensitivity corresponding to the disturbance can be estimated. After transmission through the L meter length of fiber, the phase delay of the outgoing light[3]: nlv (1) c All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-9/5/16,7:3:16)

2 Advanced Materials Research Vols Where n is the refractive index of fiber core, c is the speed of light in vacuum, v is the optical frequency. Obviously, L, v and n will result in changes in the output optical phase, it can be seen from Eq.1: nlv n L v () c n L v Phase modulation is usually caused by physical factors such as stress-strain and temperature effects [3]. the process of phase change caused by temperature effect is slow,so signal processing can be used to solve phase change caused by temperature effect. The phase change caused by stress-strain is mainly in the new optical fiber monitoring system of fluid flow in the paper. Michelson interferometer is used for phase modulation, as shown in Fig.1, the sinusoidal signal whose frequence is 8 KHz is modulated to optical piezoelectric phase modulator on an arm of Michelson interferometer,the other arm is used to detected sensing signal.the optical fiber wrapped closely around the outside wall of pipe before a total reflection grating as shown in Fig..A turbulent flow device whose inner diameter is changed is placed in front of the sensor unit to enhance turbulence intensity, When pressure field P ( x, w, t) changes in the pipe, change of fiber strain causes shift of the interferometer phase variation. Fig. 1 The principle diagram of Michelson interferometer P(x) fluid λ1 pipe sensor unit Fig. The principle diagram of the flow sensor Pressure testing principle.as the molecules of the fluid approach the pipe wall, they have kinetic energy[4-5]. This kinetic energy must be converted to another form of energy as the molecules reach the pipe wall. According to the first law of thermodynamics, some of the kinetic energy is converted to heat as the turbulent eddies dissipate, but most is converted into potential energy in the form of pressure. According to Prashu s research on turbulent flow, the instantaneous fluctuations pressure p is proportional to flow rate as shown by Eq.3. p uv (3) In the Eq.3, u is the velocity in the direction of the primary pipe axis and v is the velocity perpendicular to the pipe axis. According to introduction of in the literature [4], Eq.4 and Eq.5can be got: y p' ( x) (4) t N 1 N 1 i1 u ( t) u u i (5)

3 998 Sustainable Development of Natural Resources Since, the flow fluctuations are proportional to the pressure fluctuations and the pressure fluctuations are proportional to the pipe vibrations, it follows that the standard deviation of the pipe vibrations is proportional to the average flow rate. Modulation and demodulation techniques of phase generated carrier.interferometer output signal I can be expressed as[6] I A Bcos[ C cos t ( t)] (6) Where A is the average optical power of interferometer output signal, B A, 1and is interference fringe visibility, C cost is phase generated carrier, ( t) Dcos st ( t), Dcos st is phase variation caused by the tested signal, (t) is slow variation of the initial phase caused by environmental disturbances. Eq.6 can be expressed as with Bessel function expansion: I A B{[ [ k k ( 1) ( C) k 1 k k ( 1) k ( C)cos k t]cos( t) ( C)cos(k 1) t]sin( t)} (7) Fig.3 The block diagram of PGC The signal I tranfers this process As shown in Fig.3, so the final output of the system which contains the tested signal Dcos t is Experiment s B GH1( C) ( C) Dcos st The experimental system was built as shown in Fig.4, the pump draw water in the circulatory, and the flow is changed by adjusting the valve in the experiment, and electronic flow meter calibrates real flow value, then optical fiber fluid flow monitoring system monitor and calculate the relationship between flow value and the corresponding light intensity which is induced by pipe wall s vibration. The experimental data was shown in Tab.1.As shown in Fig.5. The experimental results have good linearity and repeatability. main channel (8) electronic flow meter optical flow meter bypass bypass valve Fig. 4. The diagram of the experimental system pump

4 Advanced Materials Research Vols Table1 The experimental data Flow[m 3 Flow /h] Ligh tintensity amplitude[v] [m 3 /h] Light intensity amplitude[v] Fig.5. Relationship diagram between flow value and the corresponding light intensity Conclusions This paper describes new optical fiber monitoring system of fluid flow used in oil well logging field in detail, and the size of fluid flow is accurately measured with non-intrusion and the information of fluid flow provides the scientific basis for the optimization of the oil and gas exploration program and increase of reservoir recovery. Acknowledgements This work was financially supported by doctor fund of shandong province: the fiber optic flow meter downhole and oil interferometer demodulation techniques (9BSC18)and sustentation fund of Sinopec Group fiber four-parameter monitoring technology of oil wells References [1] LIU Min min,zhou FengDU Zhi shun. OPTICS & OPTOEL ECTRONIC TECHNOLOGY. VOL.6(3) (8),p.18-1(In Chinese). [] Zhang Qian, Qiao Xue guang, Fu Hai wei.study ON OPTICAL COMMUNICATIONS.Vol 141(3) (7), p.58-61(in Chinese). [3] PENG Shi yu,ournal of Hunan Institute of Science and Technology(Natural Sciences).Vol() (7),p.36-38(In Chinese). [4] MATTHEWT,ROBERTPR,DANIELMAYEIS.Review of Scientific Instruments. Vol7 (4), p [5] ROBERTP,ONATHAND,ALANG. ournaloffluids Engineering. Vol.16 (4), p [6] Dandridge A,Tvcten A B,Giallorenzi T G. IEEE.Quantum Electron. Vol.18(1) (198), p

5 Sustainable Development of Natural Resources 1.48/ Research of Optical Fiber Fluid Flow Monitoring System Using Flow-Induced Pipe Vibration in the Oil Production 1.48/