Summary
Substantial foam formation was being experienced by two operators in several
heavy-oil leases in northern Alberta. This 10 to 12°API crude had a large
foaming potential and a unique foam-formation mechanism. Crude oil passed from
the wellhead through a short flowline to a pair of hydrostatically balanced and
heated storage tanks. The storage tanks heated the crude oil from approximately
50°C to 85°C. In doing so, it caused gas breakout and degassing, which resulted
in the formation of a thick, persistent foam in the top of the tanks. The foam
would enter the transportation trucks and end up at the local battery and
create carry-over and separation problems in the process systems.
Silicone antifoam products were not acceptable because of their poor
environmental profile and the influence these large molecules had at the
refinery where the crude oil was shipped for (predominantly) asphalt
manufacture.
A wide range of chemistries was tested including phosphate-based products,
ethoxylated and propoxylated esters, polyethylene glycol esters and oleates,
alcohols, fatty alcohols, and ethoxylated and propoxylated alcohols. One of the
major challenges detailed in this paper is that all products had to be freeze
protected to −40°C. This was significant because many antifreeze chemicals
affect the efficacy of antifoam chemicals.
This paper details evolution of testing leading to the field application of
this combined defoamer/antifoam chemistry. Initial laboratory screening is
included, which describes a laboratory test method designed to mimic the
foam-formation environment in the field more accurately. The paper also
illustrates the field-trial evaluation, as well as the case histories of full
field implementation of the highest-efficacy products.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
13 July 2008
- Meeting paper published:
20 October 2008
- Revised manuscript received:
9 January 2009
- Manuscript approved:
23 January 2009
- Published online:
8 October 2009
- Version of record:
1 March 2010
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