Summary
This paper discusses challenges related to emulsions that have been
encountered in a large Saudi Arabian field. The field produces from several
different reservoirs with a range of fluid properties. These properties provide
an interesting case of operational challenges in oil/water separation,
including increased incidents of shorting in the separator, tripping of
equipment, and increased demulsifier consumption.
This paper presents the results of a comprehensive study that was initiated
to understand the main causes of emulsion formation in the field and ways to
optimize oil/water separation. The effects of several recommendations that were
implemented by operations engineering in the field were evaluated. These
include the conversion of a two-phase separator into a three-phase separator,
splitting of the demulsifier injection between offshore producing platforms and
onshore wet-crude handling facilities, and field trials with promising
chemicals. The demulsifier costs have been reduced by more than 50% by the
implementation of retrofitting and proper demulsifier-injection strategies. The
results presented in the paper provide invaluable operational experience, and
many lessons learned are applicable to any crude-oil-treating facility.
Introduction
Crude oil has to be separated from produced water at wet-crude handling
facilities or gas/oil separation plants (GOSP). The GOSP typically produces dry
crude, gas, and water. The incoming oil and water can form an emulsion and may
be difficult to separate. When emulsions are tight, they can create a number of
operational challenges such as tripping of equipment in a GOSP, plant
instability, increased demulsifier consumption, production of off-spec crude,
and high-pressure drops in flow lines. These emulsions have to be treated to
meet crude specifications for transportation, storage, and export and to reduce
corrosion and catalyst poisoning in downstream processing.
This paper presents the case history of a Saudi Arabian field that had been
experiencing emulsion-related challenges (Kokal and Al-Juraid 1999). This field
produces from seven different reservoirs including the more viscous crude from
the “Arab” reservoirs. These oils range in viscosity from 2 cp to more than 10
cp (at 22°C), and the American Petroleum Inst. (API) gravities range from 28 to
40. The n-pentane asphaltene content varies from 0.2% to more than 7%,
and water cut for producing wells ranges from dry wells to more than 70%.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
8 January 2005
- Revised manuscript received:
8 November 2005
- Manuscript approved:
11 December 2005
- Version of record:
20 August 2006
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