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![Page 1: Plugging Wells With Hydrated Bentonite Brian F. Towler University of Wyoming Denver SPE Section, December 17, 2008.](https://reader035.fdocuments.net/reader035/viewer/2022062322/56649e4e5503460f94b4477e/html5/thumbnails/1.jpg)
Plugging Wells With Hydrated Bentonite
Brian F. Towler University of WyomingDenver SPE Section, December 17, 2008
![Page 2: Plugging Wells With Hydrated Bentonite Brian F. Towler University of Wyoming Denver SPE Section, December 17, 2008.](https://reader035.fdocuments.net/reader035/viewer/2022062322/56649e4e5503460f94b4477e/html5/thumbnails/2.jpg)
Outline
• Introduction• Advantages of Bentonite Plugs• Previous Work• Experimental Procedure• Experimental Results• Conclusions
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Permanent abandonment well schematic
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Temporary abandonment well schematic
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Advantages of Bentonite Plugs
• Heals itself if disturbed• Immune to seismic events,
deformation of casing, salt intrusion etc.
• Workover Rig often not required• Cheaper
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Previous Work
• James (1984-96) Wyoming OGC• Wheaton et.al. (1994) Montana BOM• Ogden and Ruff (1989-1992) CSU• Towler and Ehlers (1997)• Englehardt et al. (2001) Chevron• Clark and Salsbury (2003) Chevron• Idaliu et al. (2004) Chevron
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Gulf of Mexico History
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Annual number of wells permanently and temporarily plugged and abandoned in the
GOM (1947–2006)
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Average P&A aggregate cost per well ($1000/well), 2002–2007
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Field Trials in California
• Performed in Coalinga, California by Chevron Environmental Management Company in 2001
• Well included primary producers, waterflood producers/injectors, and steamflood producers
• Three generalized abandonment designs
• 19 total wells
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Case 1
• No Freshwater• 25 ft plug at
surface• 100 ft plug at
top of perforations or liner top
• 11 wells
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Case 2
• Freshwater present
• Cement in annulus covers freshwater
• 100’ bentonite needs to cover freshwater interface, 4 wells
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Case 3• Freshwater
present• Cement in
annulus does not cover freshwater
• Cavity shot is required
• Completed in two phases
• 4 wells
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Field Results
• All 19 of the plugs met California’s Department of Conservations Division of Oil, Gas and Geothermal Resources (DOGGR) approval
• Hydrating time of bentonite was observed to be affected by water temperature
• Bridging observed with bentonite nodules
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Field Trial in Australia
• Barrow Island field, Windalia Reservoir
• Single trial in 2002• Planned to apply it to a 100 well
abandonment program.
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Plugging cost comparison (Australia)
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Some Problems
• In oil and gas wells with standing water column granulated bentonite can swell and bridge off when it hits the water column, creating a plug at the wrong location.
• Integrity and strength in Saline Water is unproven
• Temperature Effects unproven
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Bentonite bars
• We have developed compressed cylindrical bullet shaped bentonite bars as a plugging product, designed to overcome the bridging problem.
• Salinity and Temperature effects being investigated in lab.
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DROP DIRECTION
8.25” LENGTH
2.7
5”
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8.25” LENGTH
4”
1.2
5” H
OLE
DROP DIRECTION
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Characteristics• Material: Sodium Bentonite• Granulation: 5/16-3/8”• Binding Agent- Water Soluble • Forming under high pressure• Length of the Bars: 8.25” (29.55 mm)• Diameter: - 2.75”( 69.8 mm)- No hole; Weight: approx: 2 kg - 3.5” ( ¾” dia. axial hole) - 4.00 ” dia.
- 4.00” ( 1” dia. axial hole); Weight: approx: 3.6 kg. Other options at request
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Pressure Containment
• Important question to answer. • What pressure differential can
the bentonite plug withstand?
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Theory: Towler and Ehlers (1997)
• Where• H = height of bentonite plug• D = diameter of plug
• Kb = friction factor
• γb = SG of Bentonite
• ρw = density of water
][24 2
HLD
H
D
HLKP bww
bwwb
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Hence Plot
D
H
D
HLVersusHLP bw
wbww
224][
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Towler and Ehlers Results
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Towler and Ehlers Results
• Friction Factor, Kb = 0.8
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Density of Bentonite
• Brunton (1988): the density of bentonite particles is 2.457 g/cc
• Clark and Salsbury (2003): compressed bentonite nodules as 2.05-2.2 g/cc.
• Englehardt et al. (2001) hydrated bentonite density: 1.75 g/cc.
• Towler and Ehlers (1997) hydrated bentonite1.616 g/cc
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Density of Bentonite
• Our Results:• Compressed: 2.31 g/cc• Hydrated: 1.489-1.846 g/cc
(depends on moisture content)
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Experimental setup
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Diam 6”
PIPE ID
3 BENTONITE PLUGS
Diam 2.75” / 8.25” LONG
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Conclusions
• Compressed bentonite bars have shown a friction factor for hydrated bentonite plugs in steel casing of 1.886.
• This compares with previously measured values 0.8 for hydrated bentonite pellets in steel.
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Conclusions
• The friction factor is function of the moisture content of the hydrated bentonite contributing to scatter in the friction factor plot.
• Expansion of the bullets (or bars) of 85% to 300% was observed when hydrated.
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Conclusions
• The density of the hydrated plugs varied from 1.489 to 1.846 g/cc depending on the moisture content.
• It is expected that these bars will be effective for sealing pressures in the plugging and abandonment of oil and gas wells.