Investigation On The Mechanism Of Deposited Water Displaced By Flowing Oil In Inclined Products Oil Pipeline

Blockage of the pipe line equipment (e.g., filters, valves) caused by corrosion of the pipe in the presence of water accumulated at low level locations along the products oil pipeline had happened many times in china. This problem becomes more and more urgent to be solved effectively to avoid leakage or blockage of the flow. In this paper, the solution of carrying water by flowing oil has been proposed to reduce the blockage resulted from the wall-deposited inner corrosion products. The mechanism of water displaced by flowing oil in hilly terrain tube has been investigated by three approaches, i.e., experimental measurement, theoretical analysis and numerical simulation. The distribution of water flushed by flowing oil, the critical condition of water carried into the upward inclined tube from lower horizontal tube by flowing oil and the prominent parameters of the critical condition have been analyzed. It is significant to instruct how to remove the accumulated water in some low spots in products oil pipelines. The main contents and conclusions of this study are as follows.The distribution of water under the shear force from flowing oil has been carefully observed on the transparent hilly terrain test loop. The water is found to behave as an eccentric water drop with very low velocity near the lower tube wall as a result of the gravity. The water distribution has been discoved to be mainly affected by the oil velocity. For example, water under very low oil velocity will spread along the horizontal tube and accumulate to the downstream as an eccentric drop. As the oil velocity increases, the eccentric water drop will become shorter with a gradient water height profile in the direction that oil flowes as a result of more intense shear. When the oil velocity further increases, the interface becomes wavy, and there will be some water separating from the eccentric water drop as small or large water drops if the wave intensity becomes strong enough. The water height model in the horizontal tube deduced in this paper shows that water height will become gradient if flushed by flowing oil. At the same time, the numerical simulations also show an excellent agreement with the observed phenomena.The amounts of water withdrawn from different tapping points evenly distributed on the lower wall of the upward inclined tube have been measured. It shows that the amount of withdrawn water changes significantly as oil velocity varies. There is no water withdrawn from the tapping valve if the oil velocity is less than the critical value. Otherwise, the amount of withdrawn water increases rapidly with the oil velocity equaling the critical value. After the oil velocity becomes large enough, all the water would be withdrawn. Meanwhile, the critical superficial oil velocity at which water would be carried into the upward inclined tube from lower horizontal tube by flowing oil has been measured and analyzed. It shows that the critical superficial oil velocity is dependent upon the tube diameter, upward inclination and water holdup. In addition, the critical superficial oil velocity has been predicted by the water height models proposed in this study, i.e. the water slug model in the horizontal tube and the eccentric water drop model in the upward inclined tube, and two competing mechnisams named interface stability analysis and dispersion model. The comparison indicates that the water height model presents a good agreement with measurements while the other two models show much higher results. According to the water slug model, the critical superficial oil velocity increases exponentially with the diameter, and its increasing rate depends on the oil flow regime. When Re_os<2000, its increasing rate becomes larger as water holdup increases; When Re_os≥2000, its increasing rate is a constant 0.63.2D simulations have been conducted to analyze the water distribution, the critical superficial oil velocity in test tubes as well as their major impact parameters by FLUENT. The water distribution is dependent on tube structure, the superficial oil velocity, water holdup and physical properties while the critical superficial oil velocity which is very sensitive to the tube diameter depends upon tube structure, water holdup and physical properties. If the diameter, inclination angle and physical properties were kept unchangeable, the critical superficial oil velocity decreases and its decreasing rate reduces as water holdup becomes larger. If the inclination angle, physical properties and water holdup were kept unchangeable, the critical superficial oil velocity increases exponentially with the diamete. If the diameter, inclination angle and water holdup were kept unchangeable, the critical superficial oil velocity reduces as oil density and viscosity increases, while the wall wetting and interfacial tension show much less effect. If the diameter, physical properties and water holdup were kept unchangeable, the critical superficial oil velocity decreases and its decreasing rate reduces as the tube upwards becomes more inclined. After the inclination angle is large enough, the critical superficial oil velocity showes tinily variable.