Wax precipitation characteristics of high pour-point live oil under high pressure

At present, the achievements in research of dead waxy oil always exaggerates the impact of wax precipitation, and the design for reservoir development or gas pipeline transportation is too conservative. However, under high pressure, the research of wax precipitation characteristics is faced with such shortcomings as single test method, low test pressure and large test temperature difference. This paper proposes a new method for predicting the wax precipitation characteristics of live oil with high wax content based on laser method. Firstly, with the use of laser, this method obtained the power of the laser transmitted though the fluid curve of live oil and dead oil; secondly, based on Beer-Lambert law under different conditions, the scale of laser power attenuation curve was unified; finally, based on the research results of dead oil, the wax characteristics under high pressure and dissolve-gas conditions were studied and analyzed, while a set of high-pressure sampling device was designed to verify the reliability of the prediction results. The experiment shows the test results obtained by the laser method are highly accurate; the dissolved gas can effectively reduce the wax precipitation point temperature and freezing point temperature of high wax content crude oil; the average wax precipitation rate under reservoir conditions is reduced by 19% as compared with ground condition. When the pressure is above the saturation pressure, the decreasing range of wax precipitation point is the largest when the pressure is in the range of 12-18 MPa, while the freezing point is almost unchanged when the pressure is below 15 MPa. The average diameter and width coefficient of equal area circle of wax crystal particles respectively tend to rise and decline in fluctuation. When the pressure is lower than 15.8 MPa, the asphaltene will precipitate in a dispersed state, affect the wax precipitation characteristics of crude oil, and can accelerate the gelation process of crude oil while inhibiting the precipitation of wax crystals. © 2019, Editorial Office of ACTA PETROLEI SINICA. All right reserved.