Water production is controlled by the size and distribution of water
saturation around wells. A recent discovery shows that not employing
hydrodynamic mixing in numerical simulators may underestimate the water
transition zone (Duan and Wojtanowicz 2006). This paper reports continuing
research into mechanisms causing expansion of the water-saturation transition
zone (transverse dispersion) in a segregated flow of oil and water approaching
a vertical well's completion. The mechanisms--including nonlinear flow,
turbulence, shear rate, and flow baffling at grains--all contribute to the
instability of the oil/water interface, resulting in hydrodynamic mixing.
Interface instability because of shearing rate has been demonstrated in our
recent study on the Hele-Shaw model (Duan and Wojtanowicz 2007). In this paper,
we mathematically model the effect of flow baffling and demonstrate transverse
dispersion experimentally using a linear physical sandpack.
A simple model of tortuous flow was developed to demonstrate the effect of
two-phase-flow baffling in granular porous media. The model shows that the
change in flow momentum of the two fluids at the point of collision with rock
grains becomes the major factor causing water dispersion.
A series of segregated-flow runs (top, oil; bottom, water) was carried out
using a physical model packed with different porous media at a constant
pressure drop. The runs were videotaped and analyzed for saturation
distribution using a color-intensity-recognition software. The results clearly
demonstrate onset of transverse dispersion of water into the flowing oil.
Further dispersion, however, was overshadowed by the dimensional and end-point
effects of the model. With a numerical estimation procedure, the initial
dispersion rate--computed from the 1D flow model--is the essential data needed
to estimate total dispersion in radial inflow to wells.
© 2010. Society of Petroleum Engineers
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- Original manuscript received:
12 July 2008
- Meeting paper published:
22 September 2008
- Revised manuscript received:
8 July 2009
- Manuscript approved:
22 September 2009
- Published online:
9 June 2010
- Version of record:
22 June 2010