Research On Water Hold-up Measuring Techniques Based On Surface Plasmon Resonance

Surface plasmon resonance (SPR) is an optical sensing technology that has drawn much attention in recent years. It is extremely sensitive to the refractive index of external media, and it has great potential application in many fields such as physics, chemistry, biology fields and so on. SPR has main feature of high sensitivity, label free, which can be conducted in real time and have no interruption of background. With the rapid development of SPR, expanding applications has become one of the major trends. Since the technology of horizontal and highly deviated wells has been widely used, the flow state of multiphase fluid has obviously changed in oil wells. The problem of high water concentration of oil wells and oil-water two-phase flow is becoming worse, leading to that the current measurement method of water hold-up has a large measurement error and its sensitivity decreases. By making use of the difference of refractive index between oil and water, water hold-up has been investigated by means of SPR technology in the laboratory. The purpose of this study is developing a new measurement method of water hold-up for oil field application.In this study, Au thin film was deposited onto the bottom of triangular by means of magnetron sputtering technology, which was used to be as the sensor component of Kretschman structure SPR sensor. And the water hold-up of different concentrations oil and water mixture was measured through SPR system. It is found that the film thickness, prism and the external media have remarkable influence on resonance angle. The intrinsic connection between oil-water water hold-up and the resonance angle has been clarified.The simulation results show that the phenomenon of surface plasmon resonance produces the most obvious phenomenon are at about 50nm of gold film thickness. And the bigger difference between the prism and the refractive index is, the smaller the SPR resonance angle, and the higher the sensor sensitivity is. It is seen that the surface plasmon resonance angle becomes bigger and its peak becomes wider with the increases of the refractive index, thus, the sensor's sensitivity are decreased.The experimental results show that the impact on the angle of the surface plasmon resonance by the refractive index of prism is obvious. With the increasing of refractive index difference between external media and prism, the resonance angle is becoming smaller, which is similar with the results simulated. When the oil-water concentration changed gradually from 5% to 45%, the spectral lines of surface plasma resonance shifted to the right, and the resonance angle increased. Moreover, the changes between oil-water hold-up and the refractive index or resonance angle have a linear relationship. It is a new way to measure oil-water hold-up by means of SPR technology. This study will play an important role in oil field production and it is worthy of expanding SPR application areas and developing a novel type of water hold-up sensors.