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An Experimental Study on the Effects of Heat and Chemical Inhibitors on the Flow Behaviour of Waxy Crude Oils. The Effects of Heat and Chemical Inhibitors on the Rheological Properties of Waxy Crude Oils with regard to Pumping in Pipelines
Mohamed, Fathia A.B.
Mohamed, Fathia A.B.
Publication Date
2019
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The University of Bradford theses are licenced under a Creative Commons Licence.
Peer-Reviewed
Open Access status
Accepted for publication
Institution
University of Bradford
Department
Faculty of Engineering and Informatics
Awarded
2019
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Abstract
Waxy crude oils (1/3 of oil produced worldwide), pumping through
pipelines considered risky operation due to the crude wax content (15-40
wt.%) and to the temperature at which wax supersaturates and precipitates,
leading to the danger of pipe blockage, eventually resulting, in multimillion
dollars loss in production and maintenance.
This research undertaken to develop operational strategy of waxy crude
pipelines, considering the crude and crude gel properties and flow conditions.
The research problem was approached by characterizing the crude gel with
and without additives using chromatography (GC), differential scanning
calorimetry (DSC), cross polarised microscopy (CPM), controlled stress and
oscillatory shear rheology (CSR and OSR), the principal parameters being the
crude temperature and the rate at which the crude was cooled. GC and DSC
were useful in establishing wax composition, content and wax appearance
temperature (WAT). Control stress rheometer proved to be the most
appropriate as it measured the reduction in apparent viscosity at full production
(10-50 s-1 shear rate), near shutdown (1 s-1
) and yielding when the oil was
statically cooled. On this basis, it was established that the wax inhibitor was the most effective. CPM revealed that only the wax inhibitor changed the
structure of the gel, disrupting its otherwise knitted crystal network. Dilution
with the light crude oil merely reduced the wax content and the pour point
depressant reduced the gelling temperature. OSR provided a check on CSR
and confirmed the gelation temperature measured. CSR provided the yield
stress measured, it also provided comprehensive data that can be used for
theoretical modelling of this complex flow.
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Type
Thesis
Qualification name
PhD