Estimation of deposit thickness in single-phase liquid flow pipeline using finite volume modelling

Abstract

A significant problem with liquid pipelines can be the internal deposition of wax, sediments, tuberculation and biofilms which results in decreased flow assurance of the pipelines and higher pumping costs in addition to safety issues. Therefore, it is very important to monitor the deposits and roughness in the pipelines for the timely restoration of the intended supply. This paper proposes a finite volume model (FVM) based on an implicit flux limiter-Riemann solver (CLAWPACK) to estimate deposit thickness in oil and water pipelines. The novelty of the proposed method is that a snapshot of transient pressures along the pipeline only at a particular time instant (end of simulation) is considered in contrast to the widely used pressure time series for comparison between computed and measured pressures to detect changes in internal diameter and wall friction. The Newton-Raphson Method is used to iteratively estimate the deposition thickness to produce an equivalent response obtained from the pressure measurements of the physical pipeline system. The proposed methodology is applied to three operating crude oil pipelines and the maximum error found between computed and measured pressures and deposit thicknesses are 0.035% and 5 mm respectively. The results indicate that the proposed model is an accurate, efficient, faster and cost-saving alternative to complex invasive type pipeline assessment techniques.