Study On Compression Properties Of Crude Oil Based On Ultrasonic Testing

One of the key problems in the design and operation process of waxy crude oil pipeline is to ensure the safety of the pipeline restartafter shutdown.The compressibility coefficient and pressure wave velocity are the key parameters in calculating the restart hydraulic process of pipeline.However,the factors such as the change of the temperature,pressure and structural strength have rarely been incorporated into the research.If the ultrasonic velocity and the density of crude oil are measured,the compressibility coefficientand pressure wave velocity can be calculated by considering the elasticity of the pipe and theoretical formula.Based on this,a gelled crude oil ultrasonic testing device was designed and built,the calibration and precision calculation of the equipment was completed,and a new method to test and process compression factor with high precision was found in this paper.Using this device to measure the compressibility of a variety of waxy crude oil and to study the influencing factors of its parameters.The study mainly includes the following three parts:(1)The compression coefficient values of crude oil from Shengli,Sudan,Boxi and Nanyang were measured under high and low temperature respectively.Considering the wax content with compression coefficient values,it was found that the more wax content is,the smaller compression coefficient value will be.(2)Based on the experimental data,the influences of temperature and pressure on ultrasonic wave velocity,density and compression coefficient were analyzed,and function relational expressions of the three parameters with temperature were fitted under different pressures.It was found that the ultrasonic wave velocity and density show negative linear correlations with different slopes when the temperature is high and low range.Also,the ultrasonic wave velocity and density increase as pressure increase,and they show linear correlation under same pressure.The reciprocal of compression coefficient is cubic polynomial function with temperature,and it decreases as temperature decreases or pressure rises.(3)The ultrasonic velocity of Shengli and Boxi crude oil and their related parameters inthe constant temperature static process and constant temperature during the shearing process under different temperature were studied.The results showed that in the static process under constant temperature below the gelled point,the ultrasonic velocity of waxy crude increases gradually with time and finally comes to be a stable value;while in the constant temperature shearing process,the ultrasonic velocity decreases graduallywith time and finally gets to a stable value.In conclusion,asthe structure of waxy crude oilgetstronger,the ultrasonic velocity isbigger,the signal voltage value is smaller,and the ultrasonic attenuation is more significant.