Summary
The redistribution of stresses around a fractured vertical well has two
sources: opening of propped fracture (mechanical effects) and production or
injection of fluids in the reservoir (poroelastic effects). In this paper, the
coupling of both phenomena was numerically modeled to quantify the extent of
stress reorientation around fractured production wells. The results have been
compared to field data from the Codell tight gas formation and analyzed for
their impact on refracturing operations.
For previously fractured wells, a secondary fracture may be initiated
perpendicular to the first fracture if a stress-reversal region is present.
Altered-stress refracturing makes it possible to access zones of the reservoirs
that are less depleted, thus increasing well production and reserves.
The results of our model quantitatively agree with previous tiltmeter
measurements, confirming the existence of refracture reorientation in the
Codell formation. The performance of refracturing treatments has been observed
to be highly variable in the Wattenberg field (Colorado), with some wells
underperforming while others are restored to initial production rates.
Historical production from neighboring wells and initial fracture performance
were shown to impact the potential benefits from refracturing predicted by the
numerical model.
This paper introduces a 3D model, coupling mechanical and poroelastic stress
reorientation used to interpret tiltmeter measurements and historical
production in the Codell tight gas formation. Guidelines are drawn from the
Wattenberg field case study that allow an operator to select candidate wells,
choose the timing of the refracture operation in the life of the well, and
evaluate the potential increase in well production after refracturing.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
5 October 2010
- Meeting paper published:
19 September 2010
- Revised manuscript received:
5 September 2011
- Manuscript approved:
20 November 2011
- Published online:
7 November 2012
- Version of record:
13 November 2012
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