Study Of The On-line Measurement System Of The Water Content In Crude Oil

With the unceasing exploitation of the crude oil, the oil content becomes lower and lower, and the water content is increasing. In order to achieve higher efficiency in oil extraction, a high accuracy, wide measurement range, and low price of water content measurement system in crude oil is needed. At present, although there are many methods were used on the measurement of water content in crude oil, most of them have disadvantage of smaller measurement range or higher cost. They are not suitable for high water content measurement.The article describes the study actuality and development trend of water content measurement in crude oil. The commonly used methods for measuring water content are systemic introduced. Based on the comprehensive comparison and analysis of the various capacitance sensors, the coaxial cylindrical capacitance sensor is used for measurement of the capacitance detection. In view of the actual situation that most oil fields in China into the exploitation phase of high water content, the coaxial capacitance sensor is improved design, which can better measure the higher water content. When complete the comparative analysis of the measurement methods and improved design of traditional capacitance sensor, the on-line measurement system of the water content in crude oil is built, and the hardware circuit and software design are introduced in detail. Hardware design includes that capacitance-voltage conversion circuit, temperature measurement circuit, LCD circuit, keyboard circuit, serial communication circuit, voice alarm circuit and power supply circuit which provides a stable voltage for the entire system. Software design includes that the main program design, data collection subprogram, data processing subprogram, interrupt subprogram and temperature compensation. Because of the capacitance of the capacitance sensor is smaller and more disturbances during the measurement course, the accuracy is not high. In response to the shortcomings, the integrated chip CAV424 is used for data collection and conversion. The temperature sensor DS18B20 is used for real-time detection of the temperature for temperature compensation. Taking into account the influence cause by fouling and wax of electrodes surface during the measurement of the water content, the automatic cleaning device is installed for cleaning timely in the system.Finally, preliminary tests are carried through. The system can measure the water content of 0-100%, particularly can measure the higher water content linearly and accurately. After increase the temperature compensation, the overall system error is less than 2%, even below 1.5% of the higher water phase. The test results proved the feasibility and reproducibility of the on-line measurement system of the water content in crude oil. The measurement results can also be used for accurate estimation of crude oil production, controlling the state of oil wells, prediction of oil field development life, reducing resource consumption effectively and reducing production cost. We can make a step to the automated management of crude oil exploitation. And the system design is less expensive, it suitable for general application in the industry of crude oilexploitation.