Influence of pour point depressant on wax crystal morphology of crude oil

Variety of wax crystal morphology in crude oil under different addition amount of pour point depressant (PPD) was observed by micropolariscop and the number and diameter of wax crystals were analyzed by image software to realize quantitative description of wax crystals size and distribution. With the OMA addition amount increased, the wax crystals of crude oil became shorter and smaller with even size, and well dispersed from irregular, flake and rod-like. The content of wax crystals with the diameter of 2-5 μm increased from 8.5% to 95.6%, while the content of wax crystals with the diameter of 9-13 μm decreased from 67.5% to 0.01%. It was shown that the PPD could inhibit the formation of wax crystals network, thus the system energy decreased and the possibility of forming space net structure became less, and rheologic behavior was improved. The relation of PPD dosage added in crude oil with average diameter of wax crystals and magnitude of pour point depression could be determined by nonlinear fitting, which was in accordance with the testing results.