Research Of Gas Liquid Separate Crude Oil Water Cut Measurement System

Crude oil water-cut is one of the important parameters of the petrochemical industry, which impacts directly on the extraction, dehydration, measurement, metering and other related links of crude oil. With the oilfield development for many years, the water-cut of crude oil become higher and higher, then developing a system with high measurement precision, wide measuring range, low price and can adapt to bad environment is necessary to improve the efficiency of oilfield. However, oil and water two phase flow is a very complicated process, the measurement of water-cut is very difficult, and still now there is not a universal measuring system, the real-time accurate measurement of crude oil water-cut is urgent to be solved.By comparing various detecting methods at home and abroad, analyzing their advantages and disadvantages, finally selected the capacitance sensor to detect water-cut, and through the argumentation, improved part design of capacitive sensor. And then demonstrated the feasibility of the capacitance method with a small amount of gas. Aiming at the complex structure of traditional capacitance sensor in detection of crude oil water-cut and the problem that the measuring process is vulnerable to be influenced by parasitic capacitance and temperature of external environment, the paper proposed a new design scheme of hardware circuit based on capacitance to voltage conversion chip CAV444. Through the experiment verified the CAV444 capacitance to voltage conversion performance, and analyzed the influence of temperature on the system. Then calibrated the capacitance sensor, and used a variety of methods to make curve-fitting based on the calibrated data, at last selected Fourier function fitting method through comparing. The experiments in laboratory confirmed that the system can realize the measurement of water-cut from 0% to 100%, for the vast majority of the system error within 2%, and repeatability of the system is very good that can meet the requirements of industrial field, and the system design is less expensive, it suitable for general application in the industry of crude oil exploitation.