Plug &amp; abandonment of offshore wells: Ensuring long-term well integrity and cost-efficiency

Vrålstad, Torbjørn; Saasen, Arild; Fjær, Erling; Øia, Thomas Monge; Ytrehus, Jan David; Khalifeh, Mahmoud

doi:10.1016/j.petrol.2018.10.049

Cited by 210 publications

(66 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Effective plugs may be installed by reaming the drillhole over a relatively short section, which is preferably located adjacent to a clay, shale or salt rock layer. The reamed drillhole section will be filled with a suitable backfill material, which will be compacted by the overburden and plastic deformation of the surrounding rock [50,51], effectively isolating the disposal section from the surface and at the same time sealing the excavation disturbed zone. Similar plugs may be installed throughout the disposal section to compartmentalize the disposal section, reducing the risk of axial radionuclide transport to transmissive zones that may intersect the drillhole.…”

Section: Backfilling and Sealingmentioning

confidence: 99%

Disposal of High-Level Nuclear Waste in Deep Horizontal Drillholes

Muller

Finsterle²,

Grimsich

et al. 2019

Energies

View full text Add to dashboard Cite

Spent nuclear fuel and high-level radioactive waste can be disposed in deep horizontal drillholes in sedimentary, metamorphic or igneous rocks. Horizontal drillhole disposal has safety, operational and economic benefits: the repository is deep in the brine-saturated zone far below aquifers in a reducing environment of formations that can be shown to have been isolated from the surface for exceedingly long times; its depth provides safety against inadvertent intrusion, earthquakes and near-surface perturbations; it can be placed close to the reactors and interim storage facilities, minimizing transportation; disposal costs per ton of waste can be kept substantially lower than for mined repositories by its smaller size, reduced infrastructure needs and staged implementation; and, if desired, the waste could be retrieved using “fishing” technology. In the proposed disposal concept, corrosion-resistant canisters containing unmodified fuel assemblies from commercial reactors would be placed end-to-end in up to 50 cm diameter horizontal drillholes, a configuration that reduces mechanical stresses and keeps the temperatures below the boiling point of the brine. Other high-level wastes, such as capsules containing 137Cs and 90Sr, can be disposed in small-diameter horizontal drillholes. We provide an overview of this novel disposal concept and its technology, discuss some of its safety aspects and compare it to mined repositories and the deep vertical borehole disposal concept.

show abstract

Section: Backfilling and Sealingmentioning

confidence: 99%

Disposal of High-Level Nuclear Waste in Deep Horizontal Drillholes

Muller

Finsterle²,

Grimsich

et al. 2019

Energies

View full text Add to dashboard Cite

show abstract

“…Cement sheaths are among the most important barrier elements in both petroleum wells and CO 2 injection wells. To prevent leakages of downhole fluids, the cement sheath needs to retain its integrity throughout the entire lifetime of the well, i.e., during the production and injection phase, and also, after well abandonment [4,8,9]. There are different types of cement sheath failure modes [10][11][12][13][14], where the two most common and well-understood are radial cracks and microannuli.…”

Section: Introductionmentioning

confidence: 99%

Digital Cement Integrity: A Methodology for 3D Visualization of Cracks and Microannuli in Well Cement

Vrålstad

Skorpa

2020

Sustainability

Self Cite

View full text Add to dashboard Cite

Leakages of greenhouse gases, such as methane and carbon dioxide from wells, may have considerable environmental consequences. Although much emphasis is currently put on understanding well barrier failures, and thus, preventing well leakages, especially for an important barrier material as cement, there are still several knowledge gaps and unknowns. However, a step-change in well integrity understanding may be obtained by applying advanced characterization techniques and scientific approaches to studying well barrier materials and their failure mechanisms. This paper describes the development of an experimental methodology that uses X-ray computed tomography to obtain 3D visualizations of cracks and microannuli in annular cement sheaths. Several results are included that demonstrate the value of using such digital methods to study well cement, and it is shown that such experimental studies provide an improved understanding of cement sheath integrity. For example, it is seen that radial cracks do not form in symmetrical patterns and that microannuli do not have uniform geometries. Such experimental findings can potentially be used as benchmark to validate and improve cement integrity simulation tools.

show abstract

“…CO 2 ) imposes extreme loadings on the cement sheath in both short and long-term in terms of pressure and temperature variations. Failure of cement sheath can lead to problems in the integrity of production or injection wells as well as after well abandonment [1,2]. Therefore, it is important to maintain the 1 Contact author: sohrabgheibie@gmail.com cement sheath failure.…”

Section: Introductionmentioning

confidence: 99%

Numerical Modeling of Radial Fracturing of Cement Sheath Caused by Pressure Tests

Gheibi

Sangesland

Vrålstad

2019

Volume 8: Polar and Arctic Sciences and Technology; Petroleum Technology

Self Cite

View full text Add to dashboard Cite

To achieve an acceptable level of zonal isolation, well integrity should be guaranteed in hydrocarbon production and geological CO2 sequestration. Well pressure test can cause different types of failures in the well system leading to leakages through these failures. Laboratory evidences have revealed that occurrence of radial tensile fractures is likely during pressure tests. In this paper, we use a numerical code call MDEM which was formulated based on discrete element method. The code can model discontinuum feature of fractures. A model of a lab-sized pressure test was built and compared to an experiment previously published. The model was tested under different confinement levels and effect of the tensile strength of rock on the radial fracture was investigated at the same lab-scale. Fracture opening profiles are also presented showing the leakage potential of these fractures under different pressure level.

show abstract

Plug & abandonment of offshore wells: Ensuring long-term well integrity and cost-efficiency

Cited by 210 publications

References 32 publications

Disposal of High-Level Nuclear Waste in Deep Horizontal Drillholes

Disposal of High-Level Nuclear Waste in Deep Horizontal Drillholes

Digital Cement Integrity: A Methodology for 3D Visualization of Cracks and Microannuli in Well Cement

Numerical Modeling of Radial Fracturing of Cement Sheath Caused by Pressure Tests

Contact Info

Product

Resources

About