Abstract
Hydrogen sulfide breakthrough in producing wells occurred after the
breakthrough of CO2 in the Long Coulee Glauconite F reservoir in southern
Alberta, where acid gas (98% CO2, 2% H2S) has been injected since 2002. It was
hypothesized that the preferential solubility of H2S in formation brine is
responsible for the delay in H2S breakthrough.
To study the chromatographic separation of H2S and CO2, a series of
experiments were conducted to measure the solubility of CO2 and H2S in
formation brine at in-situ conditions. Immiscible displacement experiments were
performed in a slim tube packed with silica sand to study the breakthrough
behaviour of different gas components. The experiments were then modelled using
a compositional simulator, and the effect of different factors on the delayed
breakthrough of H2S was examined using a series of sensitivity studies.
It was confirmed that the preferential solubility of H2S over CO2 leads to
it being stripped off at the leading edge of the gas displacement front,
resulting in its delayed breakthrough. A similar delay in H2S breakthrough
occurs even at higher H2S concentrations (e.g. 30%) in the injected gas.
Through the simulation studies it was shown that the delay in H2S breakthrough
becomes more pronounced if the gas front is more diffusive. For example, it was
shown that, when gravity forces or mobility ratio favour stable displacement,
CO2 and H2S breakthroughs occur closer to each other.
This is of significance, particularly for monitoring of impure CO2 storage
in deep saline aquifers, where the impurity may consist of H2S. Detection of
CO2 at a monitoring well would indicate that the more noxious H2S is likely to
show up after some time lag. This paper describes the experiments and the
simulation studies and presents the implications of the chromatographic
partitioning of H2S and CO2 for geological storage of acid gas or impure
CO2.
© 2009. Society of Petroleum Engineers
View full textPDF
(
1,004 KB
)
History
- Original manuscript received:
17 March 2008
- Meeting paper published:
17 June 2008
- Revised manuscript received:
2 June 2009
- Manuscript approved:
22 June 2009
View Cart
