Summary
Many waterflood projects now experience significant amounts of water cut,
with more water than hydrocarbon flowing between the injectors and producers.
In addition to the impact on water viscosity and density that results from
using different injection-water sources during a field's life, water chemistry
itself may impact oil recovery, as demonstrated by recent research on
low-salinity water-injection schemes. It is also known that water chemistry has
a profound impact on various chemical enhanced-oil-recovery (EOR) processes.
Moreover, the effectiveness and viability of such EOR schemes is strongly
dependent on reservoir-brine and injection-water compositions. In particular,
the presence of divalent cations such as Ca+2 and Mg+2
has a significantly adverse effect for chemical EORs. Using new developments in
reservoir simulation, this paper outlines a method to couple geochemical
reactions in a reservoir simulator in black-oil and compositional modes
suitable for large-scale reservoir models for waterflood and EOR studies. The
new multicomponent reactive-transport modeling capability considers chemical
reactions triggered by injection water and/or injected reactive gases such as
CO2 and H2S, including mineral dissolution and
precipitation, cation exchange, and surface complexation.
For waterflood-performance assessment, the new modeling capability makes
possible a more-optimum evaluation of petrophysical logs for well intervals
where injection-water invasion is suspected. By modeling transport of
individual species in the aqueous phase from injectors to producers, reservoir
characterization can also be improved through the use of these natural tracers,
provided that the compositions of the actual produced water are used in the
history matching. The simulated water compositions in producers can also be
used by production chemists to assess scaling and corrosion risks. For
CO2 EOR studies, we illustrate chemical changes inside a reservoir
and in the produced water before and after CO2 breakthrough, and
discuss geochemical monitoring as a potential surveillance tool.
Alkaline-flood-induced water chemical changes and calcite precipitation are
also presented to illustrate applicability for chemical EOR with the new
simulation capability.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
10 September 2010
- Meeting paper published:
1 November 2010
- Revised manuscript received:
1 June 2011
- Manuscript approved:
3 August 2011
- Published online:
24 February 2012
- Version of record:
11 June 2012
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