Thousands of well-perforation jobs are executed successfully around the
world each month; however, certain perforation jobs require special design
considerations to minimize the risk of equipment damage, such as bent tubing
and unset packers, from perforating gunshock loads. Perforating gunshock loads
generate pressure waves in the completion fluid and stress waves in structural
components. The magnitude, duration, and timing of these waves depend on job
parameters that can be adjusted by the design engineer, such as type, length,
and loading of guns; number of shock absorbers; distance from sump packer to
bottom of guns; and distance from completion packer to top of guns. The
sensitivity of peak loads and gun-string movement to key design parameters can
be evaluated with a software tool specifically developed to predict
well-perforation-induced transient fluid-pressure waves and the ensuing
structural loads. All relevant aspects of well-perforating events are modeled,
including gun carrier filling after firing, wellbore pressure waves and
associated fluid movement, wellbore pressurization and depressurization by
reservoir pressure, and the dynamics of all relevant gun-string components,
including shock absorbers, tubing, and guns.
Existing fast-gauge pressure data from a large number of perforation jobs
were used in previous jobs to verify that predictions made by using software
simulation are sufficiently accurate, both in magnitude and time; thus, the
transient pressure loading on well components is sufficiently accurate to
predict the structural dynamics response and the associated gun-string loads.
In this paper, we present case studies that show how key elements used for
gunshock mitigation are simulated, and the sensitivity of peak loads and
deformation to gun-string elements, such as shock absorbers, gun types and
loading, tubing size and weight, and packer placement.
With this software, we evaluate the dependence or sensitivity of peak loads
and gun-string movement on/to key design parameters, and, when necessary,
design changes are made to reduce potentially unsafe load conditions. The
design verification and optimization methodology described in this paper
significantly reduces the risk of nonproductive time and fishing operations.
Key technologies described in this paper enabled the successful execution of
many deepwater high-pressure (HP) perforation jobs, including Petrobras'
Cascade and Chinook, the largest deepwater HP perforation jobs performed to
date in the Gulf of Mexico.
© 2012. Society of Petroleum Engineers
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- Original manuscript received:
24 March 2011
- Meeting paper published:
15 June 2011
- Revised manuscript received:
17 November 2011
- Manuscript approved:
30 November 2011
- Published online:
12 March 2012
- Version of record:
15 March 2012