Waxy Crude Cold Start: Assessment Through Gel Structural Properties

Abstract

Abstract During prolonged shut-down of pipeline transporting waxy crude oils and cooling, crystals of paraffins are formed within the fluid bulk and can interlock into a continuous gel-like network. Then, a restarting pressure is required to break the gel and resume flow, the resistance of gel to flow naturally resulting from its structure state. This paper addresses the understanding of the mechanisms of cold start-up of flow, through the assessment of the structural properties of the gelled oil. A set of laboratory techniques has been used to investigate the building-up of the gel structure after a cooling at rest. Two stock tank crude oils were tested for this investigation. As a result, the experimental data are combined into a description model of the development of the gel network as temperature decreases. Physical significance of Wax Appearance Temperatures is discussed from this model. It is concluded that the relevant parameters to build a structural model and understand the flow properties of these gelly oils are size, shapes (ratio axes) and number of paraffin crystals, and that they depend on temperature and cooling history. P. 729