Automatic Identification of Multi-interface in Crude Oil Tank Based on Self-adaptive Algorithm of Linearity and Recursion

A new self-adaptive algorithm based on the frequency signal of the moving transmitter was proposed and tested by the experiment, which could identify automatically the dynamic multi-interfaces of gas/oil and oil/water in the crude oil tank, and solve three tough problems to affect accurate measurement. The first, the separate process of the crude oil and water is dynamic, the interface changes inconstantly in that the input time of the crude oil with water is random and the separate process is inconstant and real-time. The second, the composition of higher density crude oil with demulsifiers is complex. The third, the demand of safety is very strict in oil field. The new self-adaptive algorithm based on the least square method is linear and recursive. The processing result of the algorithm is decided by the relative signal of the transmitter without the relationship to the absolute signal, which avoids the dependence on the absolute performance of the transmitter and the effect of the transmitter covered with the crude oil. The simple and low-cost transmitter based on the parallel plate capacitance sensor was chosen; the algorithm also can distinguish the multi-interfaces of oil/water and the pseudo-interface. The experimental data shows the interface position identified by the algorithm is accurate.