Summary
With the growing interest in low-permeability gas plays, foam fracturing
fluids are now well established as a viable alternative to traditional
fracturing fluids. Present practices in energized fracturing treatments remain,
nonetheless, rudimentary in comparison to other fracturing-fluid technologies
because of our limited understanding of multiphase fluid-loss and phase
behavior occurring in these complex fluids. This paper assesses the fluid-loss
benefits introduced by energizing the fracturing fluid.
A new laboratory apparatus has been specifically designed and built for
measuring the leakoff rates for both gas and liquid phases under dynamic
fluid-loss conditions. This paper provides experimental leakoff results for
linear guar gels and for N2/guar foam-based fracturing fluids under a wide
range of fracturing conditions. In particular, the effects of the rock
permeability, the foam quality, and the pressure drop are investigated.
Analysis of dynamic leakoff data provides an understanding of the complex
mechanisms of viscous invasion and filter-cake formation occurring at the pore
scale.
This study presents data supporting the superior fluid-loss behavior of
foams, which exhibit minor liquid invasion and limited damage. It also shows
direct measurements of the ability of the gas component to leakoff into the
invaded zone, thereby increasing the gas saturation around the fracture and
enhancing the gas productivity during flowback. Our conclusions not only
confirm but add to the findings of McGowen and Vitthal (1996a, b) for linear
gels and the findings of Harris (1985) for nitrogen foams.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
13 November 2010
- Meeting paper published:
25 January 2011
- Revised manuscript received:
16 October 2011
- Manuscript approved:
16 January 2012
- Published online:
31 July 2012
- Version of record:
7 August 2012
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