Summary
With the increasing development of heavy- and extraheavy-oil (EHO) fields,
separation operations are becoming increasingly challenging compared to
separation for conventional oil fields. For in-situ bitumen, EHOs produced by
thermal-process dehydration require solvent addition, injection of a large
amount of demulsifier additives, relatively high operating temperature, and
long retention times inside the separators. So, in order to respect
specifications on crude oil and water quality at lower cost, an optimization of
the different parameters involved in the whole process of separation becomes
necessary.
In the case of EHOs, the presence of polar heavy components, such as
asphaltenes, structured as a rigid film at the water/oil interface, limits the
coalescence phenomena and, consequently, limits the efficiency of separation by
gravity or by using conventional electrocoalescence.
The paper presents a methodology that permits the optimization of water and
oil separation in the case of an in-situ EHO (produced by thermal process). The
crude oil was first characterized in terms of rheological behavior and
interfacial properties. The dilatational viscoelastic properties of the
interface were determined from measurements performed with an oscillating
oil-drop tensiometer. Properties of emulsification were also investigated by
using a specific device called a dispersion rig that allows the reconstitution
of crude-oil emulsions under controlled hydrodynamic conditions. Then, a
laboratory procedure based on electrical stability tests (ESTs) was applied to
optimize the concentration of demulsifier required for effective water
separation.
Finally, the optimal electrical parameters were determined in an
electrocoalescer device in the presence of the selected concentration of
additive. The efficiency of coalescence was measured by following the growth of
dispersed water droplets inside the emulsion using differential scanning
calorimetry (DSC).
This methodology may be used advantageously as a useful base for further
scaleup studies concerning field separation facilities.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
18 February 2009
- Revised manuscript received:
28 August 2009
- Manuscript approved:
11 November 2009
- Published online:
3 May 2010
- Version of record:
22 September 2010
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