Suspended Particles Sensor: A New Downwell Detection Instrument for Oilfield Injection Water Based on the Mie Scattering

Suspended particles detection is an important indicator for evaluating the quality of oilfield injection water. Aiming at the measurement of suspended particles concentration and median diameter in the injection water, a downwell suspended particles sensor based on the Mie scattering is studied in this paper. The sensor is equipped with a Laser source, a set of Fourier lenses, a sampling actuator and an annular optical imaging system. The laser is the energy source of the sensor and can continuously emit a stable Gaussian beam, which can be transformed into an enlarged parallel beam after passing through Fourier lens. When the parallel beam is refracted by the suspended particles and processed by imaging lens, it will form rays of different scattering directions. Furthermore, the scattered rays is received by the detector and inversely calculated, the diameter and volume content of suspended particles is achieved. In the development of this sensor, a laser with a wavelength of 640 nm is selected, and a 4 times Fourier lens beam expansion system and a 32 -ring small-diameter detector are designed. Lab test shows that the sensor can realizes the measurement of suspended particles with a diameter of 1-100 microns, and the detection accuracy is $\pm 8 \%$.