Experimental Study On Rheological Properties Of Waxy Crude Oil In Lamadian Oilfield Of Daqing

The crystals of waxy crude oil produced in the Daqing Oilfield will form the three-dimensional network structure near the freezing point temperature of wax, and this can wrap the crude oil in liquid so crude oil lost liquidity. Gelled crude oil shows thixotropy, yield stress, viscoelasticity and other complex rheological properties. Study on the rheological properties of gelled crude oil has important significance to the production, transportation and use of crude oil.Due to the thermal history, shear history and other external factors can have a greater impact on the internal structure of waxy crude oil especially wax crystal structure, so subjected to different history the rheological properties of gelled crude oil will be changed greatly. This paper uses crude oil in Lamadian Oilfield of Daqing as experimental material. Using Hakke Mars III rheometer and HAAKE VT550 rotary viscometer, we made the shear step test, constant shear rate test and small amplitude oscillatory shear scanning test of waxy crude oil to study the rheology properties more detailed. Three kinds of conditions including constant temperature, constant temperature shearing and cooling shearing are considered and analyze the results of the experiment.The results show that for waxy crude oil of Lamadian Oilfield, when the ascending temperature rises to Newton’s temperature, the thixotropic structure of crude oil is enhanced, yield stress is increased, and viscoelastic properties is enhanced; when ascending temperature is non-Newtonian temperature(higher than measuring temperature), the thixotropic structure of crude oil is weaken, yield stress is decreased, and viscoelastic properties is waken. The lower non-Newton temperature, the more obvious the trend for thermal history. For shear history, under the experimental temperature, after constant temperature shearing, the thixotropic structure is weakened, yield stress decreases and the viscoelastic properties are weakened; after cooling shearing, when the measured temperature is higher than the freezing point, the rheological properties have almost no change; When the temperature measurement is lower than the freezing point, yield stress decreases, viscoelastic characteristics are weakened, but for the thixotropy, when the cooling shear rate is greater than the rate of test, shear stress will be smaller, the strength of thixotropic structure will be weakened, if the cooling shear rate is less than the rate of test, the thixotropy will not change.