Review of wax sedimentations prediction models for crude-oil transportation pipelines

Wax sedimentation in pipelines is a severe crude oil production and transportation challenge. Pipeline surface roughness is experienced at the early stages of the problem; with time, the effective pipe cross-sectional area is reduced due to pipeline wax plugging, causing pumping pressure increase, equipment failures, and blockages, resulting in unnecessary downtime costs and pipeline abandonments in the worst situation. This paper reviews mathematical and experimental loops models used for pipeline solid wax predictions and calculations as functions of pressure, temperature, and fluid composition; by assessing model's Assumptions, strengths and weaknesses. It is found that most mathematical models applied molecular-diffusion mechanisms in modeling and neglected shear effects; which resulted in wax over-prediction. Experimental loop was time-consuming due to mounting and dismounting of test section during wax deposition measurements; our modification has included sensor-integration to detect, measure, and analyze wax deposition; Reliable wax predictions models are essential to properly design pipelines and adopt cost-effective strategies for wax deposition prevention, control, and removal.