(459d) Simulating Wax Deposition in Pipelines with a Cape Open 1.1 Thermodynamics Package

Wax deposition from petroleum fluids is a common problem in the oil industry. It affects principally the production and transportation of crudes but may also occur with lighter fluids such as condensates. In this paper we outline the modelling components necessary to simulate wax deposition in a pipeline. Particular attention is focused on the physical property requirements for such a simulation. The situations considered range from the simplest case of an oil pipeline to the increasingly common situation where oil, gas and water phases are present in addition to the wax.

The Multiflash physical property package can model multiphase equilibria involving fluid and solid phases including waxes. It has a CAPE-OPEN Thermodynamics and Physical Properties interface that conforms with the version 1.1 specification. This latest version of the specification makes it possible to describe complex phase behaviour involving many phases and including solids like wax. We have interfaced Multiflash with a wax deposition simulator (FloWax) both directly and via a CAPE-OPEN interface. We describe our experience in implementing the interface and the important lessons learned. We show results of a number of simulations and demonstrate that it is necessary to model the wax phase in a detailed compositional way in order to get physically reasonable results. We conclude that the CAPE-OPEN 1.1 thermodynamics specification is suitable for this application but computational speed is an important consideration and interfaces must be designed with care in order to avoid unnecessary calculations and to maximise the use of available information.