Summary
During frac-pack treatments, completion hardware is often subject to extreme
differential pressures. This is especially true during early screenouts where
the large hydrostatic differentials can suddenly be placed on the completion
components, resulting in a high risk of collapse. Deep wells and
completion-tool configuration can limit supporting pressures for these
tools.
To prevent damage to completion hardware such as crossover tools, fluid-loss
devices, and blank pipe, the maximum surface treating pressure has been limited
to a calculated Pmax (Jannise and Edwards 2007). Conventionally, the
reservoir pressure was used as the internal supporting pressure in these
calculations. Using the reservoir pressure to calculate the Pmax
results in a worst-case pressure limit that prevents collapse in virtually any
job. However, today many frac-pack treatments are being performed in
low-pressure, subhydrostatic reservoirs. Many of these jobs could not be placed
using just reservoir pressure for support, even when using high-strength,
completion hardware materials.
By analyzing a significant number of actual jobs, it was determined that the
current standard equations are too conservative when compared to actual
treating results. By using less conservative, modified equations, numerous
additional wells have been completed with frac-pack technology. This paper
studies a number of these successful frac-pack jobs that could not have been
performed using the standard Pmax equation and safety factors.
Post-job bottomhole-gauge data are examined to determine the true differential
pressures and verify the accuracy of the assumptions that are used in the
modified Pmax calculation, which provides valuable insight and
recommendations for tool design, fluid properties, and maximum-pressure
limitations for frac-pack completions.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
2 February 2010
- Meeting paper published:
4 May 2010
- Revised manuscript received:
19 October 2010
- Manuscript approved:
9 November 2010
- Published online:
16 May 2011
- Version of record:
13 June 2011
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