Summary
After two decades of relative calm, chemical enhanced-oil-recovery (EOR)
technologies are currently revitalized globally. Techniques such as
alkaline/surfactant/polymer (ASP) flooding, originally developed by Shell, have
the potential to recover significant fractions of remaining oil at a
CO2 footprint that is low compared with, for example, thermal EOR,
and they do not depend on a valuable miscible agent such as hydrocarbon gas. On
the other hand, chemical EOR technologies typically require large quantities of
chemical products such as surfactants and polymers, which must be transported
to, and handled safely in, the field.
Despite rising industry interest in chemical EOR, until today only polymer
flooding has been applied on a significant scale, whereas applications of
surfactant/polymer or alkaline ASP flooding were limited to multiwell pilots or
to small field scale. Next to the oil-price fluctuations of the past two
decades, technical reasons that discouraged the application of chemical EOR are
excessive formation of carbonate or silica scale and formation of strong
emulsions in the production facilities.
Having identified significant target-oil volumes for ASP flooding, Petroleum
Development Oman (PDO), supported by Shell Technology Oman, carried out a
sequence of single-well pilots in three fields, sandstone and carbonate, to
assess the flooding potential of tailor-made chemical formulations under real
subsurface conditions, and to quantify the benefits of full-field ASP
developments.
This paper discusses the extensive design process that was followed.
Starting from a description of the optimization of chemical phase behavior in
test-tube and coreflood experiments, we elaborate how the key chemical and flow
properties of an ASP flood are captured to calibrate a comprehensive
reservoir-simulation model. Using this model, we evaluate PDO's single-well
pilots and demonstrate how these results are used to design a pattern-flood
pilot.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
6 June 2010
- Meeting paper published:
11 April 2010
- Revised manuscript received:
22 January 2011
- Manuscript approved:
25 August 2011
- Published online:
19 December 2011
- Version of record:
28 December 2011
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