Study On Fluorescence Detection Technology Of Oil Content In Oilfield Reinjection Water

Using oilfield re-injection water for oil exploitation not only avoids the waste of water resources,but also improves the economic benefits of the oilfield.However,reinjection water is a kind of multi-contaminant mixed sewage,and its quality directly affects the ecological environment of groundwater.Therefore,the quality control of reinjection water is necessary to protect the ecological environment.And the online detection of oil content in oilfield re-injection water is the key to achieve the reinjection water quality control.Traditional methods such as weighing method,gas chromatography and spectrophotometry cannot meet the needs of online detection.Although the scattering method can be applied in on-line detection,it is susceptible to suspended particles in re-injection water.The requirement of detection environment is too strict.In response to this problem,this paper develops an on-line detection method for oil content of oilfield re-injection water,based on the ultraviolet fluorescence detection technology.A modeling method of noise transfer model based on sampling spectrum aliasing principle is proposed.The noise transfer models of pulse modulation and square wave modulation are constructed.The fluorescence detection system used for the oil content of re-injection water detection is built,through which the oil content of oilfield re-injection water in the range of 100?1000mg/L can be precisely detected.The main work and innovations of this project are as follows:1.The various detection methods of mineral oil are compared.Taking into account the detection environment with narrow oil pipeline and high temperature characteristics,the method based on fluorescence effect is selected to detect the oil content in the oilfield re-injection water.According to the analysis of fluorescence spectrum of oilfield re-injection water,the ultraviolet light source which radiates light waves of 360 nm is used.The ultraviolet fluorescence detection model is established,in which the relationship between the excitation light intensity,the fluorescence intensity and the sample content are deduced.And the Influence of the scattered light of the light source on the detection results is also analyzed.2.A modeling method of noise transfer model based on the spectrum aliasing principle is proposed.The noise transfer models of pulse modulation and square wave modulation are constructed.The relationship between signal-to-noise ratio and modulation parameters is deduced,which provides the theoretical basis for the optical selection of on-line detection scheme.Based on the pulse modulation,sampling,differencing and digital filtering,the Low-power online detection scheme solves the problem that the light source is limited due to the difficulty of heat dissipation in high temperature environment.In addition,the scheme improves the transient light intensity of the light source to shorten the light-emitting time in per unit time,ensuring the signalto-noise ratio of the detection result and reducing the average power of the light source.3.Based on the pulse modulation and demodulation technology as well as the principle of ultraviolet fluorescence,an on-line detection system for oil content of oilfield re-injection water is established.A small embedded photoelectric detection probe is designed to adapt the environment of narrow pipeline space.In order to realize the stability control of the light source,a drive module based on feedback control theory is devised.And the noise optimization design of the demodulation module circuit is completed,minimizing the noise gain.Moreover,the pulse synchronous sampling control program is programed to achieve the accurate sampling of the peak value of the pulse signal.4.The experimental platform used for oil content detection is built.The experiments compare the stability of the light source with the pulse modulation method and the square wave modulation method.The results show that the square wave modulation methods and the pulse modulation method have the light intensity stability of 2.5% and 0.5% respectively within 3 hours.In addition,the working curve of reinjection water is calibrated.Finally,the on-site online detection experiments are completed.The results verify the feasibility of the system to online,precisely detected the oil content of oilfield re-injection water in the range of 100?1000mg/L and the detection results is consistent with the detection result of the weighing method.