Summary
This paper describes the development of a two-phase near-wellbore simulator
to predict the impact on squeeze lifetime of the overflush fluid type. In the
past, a single aqueous-phase model was used for a diesel overflush treatment.
The new model enables a more accurate description of the displacement process
and the impact of inhibitor transport through the formation and retention on
the rock matrix.
Field data are presented, with various treatments being considered. In each
case, the well was treated with the same aqueous scale inhibitor (SI). The
initial squeeze treatments used a diesel overflush. However, subsequent
treatments used the same inhibitor but used seawater as the overflush fluid. It
is clear from the field returns that the use of seawater rather than marine
diesel improved chemical placement and extended treatment life. The theory
behind this phenomenon is outlined, so allowing for more accurate treatment
designs.
The process followed involved first deriving an isotherm using a
single-phase squeeze model based on the water overflush treatment. This is the
established conventional approach used in many hundreds of cases worldwide.
This isotherm was then used to model the same treatment using the new two-phase
model, which accounts for saturation changes during the treatment. A good match
was achieved using the isotherm, giving confidence that the two models agree
for purely aqueous treatments. A diesel overflush treatment was then simulated
using the two-phase model and the same isotherm, and again a good match was
achieved. However, modeling the diesel overflush treatment in the single-phase
model required a different isotherm to achieve the match. This clearly
indicates that diesel overflush treatments may be modeled accurately using the
two-phase model. Additional sensitivity calculations were performed to
investigate the impact of splitting the overflush volume into separate diesel
and water stages.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
10 March 2008
- Meeting paper published:
28 May 2008
- Revised manuscript received:
31 October 2008
- Manuscript approved:
22 November 2008
- Published online:
30 July 2009
- Version of record:
8 September 2009
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