Hydraulic Testing of Compacted Bentonite Used for Plug and Abandonment Operations

Holl, Heinz-Gerd

doi:10.4236/jmmce.2019.75019

Cited by 2 publications

(1 citation statement)

References 7 publications

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“…Two, physically identical, but compositionally different plugs, with an outer di-ameter of 139.7 mm were made at the bentonite plug testing facility, University of Queensland, Brisbane, Australia. One plug was compacted using the raw bentonite material, the second one was made out of a bentonite-polymer blend [7]. The mineralogy of the bentonite material is published by Holl & Scheuermann [8].…”

Section: Sample Preparationmentioning

confidence: 99%

Small Angle Neutron Scattering Investigation of Compressed Bentonite Plugs

Blach¹,

Holl²

2019

JMMCE

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Bentonite plugs manufactured with and without a polymer binder were studied using Small Angle Neutron Scattering (SANS) and Ultra Small Angle Neutron Scattering (USANS) techniques. We have subjected the samples to hydration by evaporating water and then applied CD 4 methane at a Zero Average Contrast (ZAC) pressure (about 48.3 MPa/7000psi) to measure the accessible and inaccessible pores and channels. The data show that introduction of moisture has an immediate effect on the smallest pores, with swelling preventing access by the methane; however the larger network appears to be little affected by the addition of the moisture. The addition of a binder to the plug creates a greater number of open pores in the micron and above size regime, indicating that the polymer is vital in creating larger channels, which aids the movement of moisture throughout the plug, at the expense of sealing the smallest ones. This suggests that the polymer binder helps in the self-healing process in the clays and makes the structure more stable. The process of plug manufacturing and drying produces a chaotic system of aggregates in the sample, which forms packed clusters 130 nm in size. Addition of moisture destroys this structure. Addition of water to the dried plug material showed that at 18 weight% a dual layer of water has formed in the montmorillonite layer of the clay, separating the montmorillonite layers by 17 Å. Increase to 33 weight% of water has added an extra layer with basal spacing of 19 Å. The clay hydration with vapor and directly deposited liquid appear to delaminate some of the clay affecting the fractality index at the micron sizes. Mechanical compression had a significant effect on the polymerised sample, encouraging larger water-conducting channels to form.

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Section: Sample Preparationmentioning

confidence: 99%

Small Angle Neutron Scattering Investigation of Compressed Bentonite Plugs

Blach¹,

Holl²

2019

JMMCE

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Evaluation of Bentonite Application for the Abandonment of Deep Geo-energy Wells

Corina¹,

Wollenweber²,

Fischer³

et al. 2022

Rock Mech Rock Eng

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Hydrated bentonite is considered an alternative subsurface sealing/plugging material for deep geo-energy wells. However, the knowledge related to this application and the corresponding properties of bentonite is still lacking. This includes the mechanical properties at the interface of bentonite plugs with the adjacent materials (surrounding rock or casing steel) and the mechanical stability of plugs under downhole in-situ conditions. In this work, we performed experiments investigating the interface shear properties and shear strength of a bentonite plug under various settings for deep geo-energy applications, such as hydrocarbon and geothermal wells. The interface’s shear properties against various adjacent materials and fluid conditions were characterized. The influence of chemical exposure, the salinity of the curing fluid, fluid pH, pressure, and temperature on bentonite’s mechanical stability was evaluated in a small- and large-scale setting. The latter was performed using realistic casing sizes and placement methods, relevant for the field application. The experimental results show that the averaged shear strength of the bentonite plug interface is 13.3 kPa and 9.1 kPa when cured in freshwater and seawater, respectively. The increase in strength with increasing curing pressure, temperature, and fluid pH was characterized for the first time. The interfacial properties of cohesion and friction angle vary with different surrounding materials. They are also influenced by the saturating condition and salinity of the saturating fluid. Based on the experimental results, a bentonite plug with a minimum length of 15–43 m placed in casings of 7–5/8″ to 13–3/8″ would be sufficient to meet the necessary criteria of the Dutch regulators as an isolating material for well abandonment.

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Hydraulic Testing of Compacted Bentonite Used for Plug and Abandonment Operations

Cited by 2 publications

References 7 publications

Small Angle Neutron Scattering Investigation of Compressed Bentonite Plugs

Small Angle Neutron Scattering Investigation of Compressed Bentonite Plugs

Evaluation of Bentonite Application for the Abandonment of Deep Geo-energy Wells

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