Application of Bentonite as an Alternative Sealing Material for Deep Hydrocarbon and Geothermal Wells
conference paper
Bentonite has been identified as a cost-efficient and durable solution for alternative plugging options in shallow wells due to its ductile, self-healing, and chemically stable properties. In this work, we evaluate the application of bentonite as a sealant for deep geo-energy wells. The shear strengths of the bentonite-casing and bentonite-rock interfaces were investigated at various downhole conditions, i.e. fluid salinity, fluid saturation, pressure, temperature, and casing sizes. A sliding shear test was performed to measure the cohesion and friction angle at the interfaces of different bentonite systems. Furthermore, dislodgement tests were conducted using a custom-built test cell with realistic downhole geometry, both small- and large scale, to measure the minimum axial force to displace the plug in a casing. Results show that bentonite plug lengths of less than 50 m in casing sizes from 7-5/8” to 13-3/8” would be sufficient to meet the necessary criteria for alternative sealants from regulators. Interfacial shear capacity of the bentonite are negatively influenced by the fluid salinity. Achieving high initial shear capacity is more challenging in larger casing sizes, and curing the plug at elevated pressure and temperature can improve the initial strength. After failure occurs, rehydrated plugs are observed to self-heal and regain or surpass their initial interfacial strength.
TNO Identifier
962963
ISBN
9781713839125
Publisher
American Rock Mechanics Association ARMA
Source title
55th U.S. Rock Mechanics / Geomechanics Symposium, 22-23 June 2021, Houston, TX, USA
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