title: Study Of Fluid Flow Assurance In Hydrocarbon Production – Investigation Wax Mechanisms
Creators: name: Theyab, MA
Publisher: name: London South Bank University
Year: 2017

description: The current work is a study of wax deposition, a phenomenon that is one of
the main flow assurance problems faced by the oil industry, affecting
numerous oil companies around the world. Wax deposition can result in the
restriction of crude oil flow in the pipeline, creating pressure abnormalities
and causing an artificial blockage that can lead to reduced or interrupted
production. Wax can precipitate as a solid phase on the pipe wall when its
temperature drops below the wax appearance temperature (WAT).
The aim of this research is to study in a lab rig the influence of some of the
factors that control and affect the wax deposition process, such as pipe wall
temperature (inlet coolant temperature), flow rate, pressure drop, oil
temperature, shear stress, recirculation time of crude oil and viscosity. It
aims to study the chemical and mechanical methods of inhibiting wax
deposition in pipelines. The work also aims to simulate the multiphase flow
process in the rig for this study.
A new experimental flow loop system was built in the lab to study the
variation of wax deposition under single-phase transport through a pipe. A
series of experiments were carried out for varying inlet coolant temperatures,
flow rates and run times, while the pressure drop was monitored to evaluate
the effect of chemical inhibitors and to evaluate the effect of spiral flow on
wax deposition. Multiphase flow numerical simulations were undertaken
using OLGA software in order to study the effect of the factors that control
the wax deposition. Use of mixtures of inhibitors was evaluated, considering
their effects on the rheological behaviour of the crude oil.
The experimental results show that there is a direct relation between the
deposition time, pressure drop and wax deposit thickness, which is also
highly dependent on the temperature. The wax deposit increases as the inlet
coolant temperature decreases, even if the oil temperature exceeds the
WAT, resulting in a larger pressure drop. The wax inhibition percentage was
the highest using a combination of spiral flow with the inhibitor polyacrylate
polymer (C16-C22) due to the synergy effect of high shear stress and the
effect of an inhibitor that interferes with wax crystal growth. Three different
mixtures of inhibitors were prepared in this work depending to the inhibitors
that provide the greatest reduction in wax deposition; the mixtures of
inhibitors presented a high reduction in crude oil viscosity, even at lower
temperatures, due to interfere with wax molecules and prevent the growth
processes.
The findings of the numerical simulation, using a simulator to reproduce the
experimental results by tuning analogical properties (assumptions), show
agreement with the experimental results. This study presents the spiral flow
and the combination of spiral flow with the inhibitor polyacrylate polymer
(C16-C22) as efficient mitigation methods to prevent or reduce wax
deposition in hydrocarbon pipelines.