DEEP BOREHOLE PLACEMENT OF RADIOACTIVE WASTES A FEASIBILITY STUDY Bernt S. Aadnøy & Maurice B. Dusseault Executive Summary Deep Borehole Placement (DBP) of modest amounts of high-level radioactive wastes from a research reactor is a viable option for Norway. The proposed approach is an array of large- diameter (600-750 mm) boreholes drilled at a slight inclination, 10° from vertical and outward from a central surface working site, to space 400-600 mm diameter waste canisters far apart to avoid any interactions such as significant thermal impacts on the rock mass. We believe a depth of 1 km, with waste canisters limited to the bottom 200-300 m, will provide adequate security and isolation indefinitely, provided the site is fully qualified and meets a set of geological and social criteria that will be more clearly defined during planning. The DBP design is flexible and modular: holes can be deeper, more or less widely spaced, at lesser inclinations, and so on. This modularity and flexibility allow the principles of Adaptive Management to be used throughout the site selection, development, and isolation process to achieve the desired goals. A DBP repository will be in a highly competent, low-porosity and low-permeability rock mass such as a granitoid body (crystalline rock), a dense non-reactive shale (chloritic or illitic), or a tight sandstone. The rock matrix should be close to impermeable, and the natural fractures and bedding planes tight and widely spaced. For boreholes, we recommend avoiding any substance of questionable long-term geochemical stability; hence, we recommend that surface casings (to 200 m) be reinforced polymer rather than steel, and that the casing is sustained in the rock mass with an agent other than standard cement. We recommend that canisters be placed in a non-cased basal section of the borehole with buffer (cation adsorbent), sealants (flow blockage), and dense frictional sections (load transfer) separating the canisters. For intermediate- and low-level radioactive wastes, we recommend a similar DBP approach using waste capsules, but the isolation security level (capsule spacing, sealants, borehole interval used) can be adjusted to reflect the lower risk levels. Percussive drilling mining technology is used for guide holes and large diameter isolation boreholes. The pre-drilled, small-diameter guide hole is also used also for detailed individual borehole qualification. Oilfield technology using wireline and coiled-tubing methods forms the basis of the waste placement and isolation process. Lowering appropriately sized and equipped canisters to hole bottom using modern wireline systems, followed by the placement of buffer, seals and backfill, can be carried out with coiled tubing units. In summary, the DBP approach has many advantages linked to operational safety, DBP modularity, independent qualification of each borehole, and an unquestioned technical ability to provide seals and buffer material at the borehole scale. Geologically, choosing the best site is a key aspect of the DBP repository concept. From geomechanics, rock physics, and geophysics considerations, based on our mining, oilfield and rock mechanics backgrounds, it is our opinion that finding appropriate sites in Norway is a straightforward task, but it must be a carefully executed program involving many disciplines. i Acknowledgements Liam Kelly, BASc (2020, University of Waterloo, Geological Engineering), EIT, worked with us in organizing materials and putting together the Report, including developing some sections and finding appropriate reference material. Mr Kelly is pursuing a Master’s degree from Queen’s University, Kingston, Ontario, in Geological Engineering. Richard E. Jackson, PhD, PEng, vetted the Report independently. He has a long career in nuclear waste management and geological sequestration for radioactive materials, and this is key to his assessment of this Report. He helped found the firm Geofirma Engineering Ltd. (Ottawa, Ontario) that led the Deep Geological Repository site investigations for Ontario in the period 2005-2015, and the firm was recently awarded (2020) the work program for the next repository site studies for low- and intermediate-level radioactive wastes. Dr Jackson remains active in his retirement and is an Adjunct Professor at the University of Waterloo, Waterloo, Ontario. Authors Bernt S. Aadnøy, PhD, PE, is a Professor of Petroleum Engineering at the University of Stavanger, and is also Adjunct Professor at the Norwegian University of Science and Technology (NTNU). He works mainly on all aspects of well engineering, drilling, geomechanics, production and reservoir engineering, smart well technology and automation. Before transiting to academia he worked many years in oil companies, and have strong ties to applied problems. He has published more that 300 articles and have authored or co-authored 8 books, amongst them Modern Well Design, Petroleum Rock Mechanics, Mechanics of Drilling and Multivariate Optimization in Well Engineering. He was editor of the SPE Advanced Drilling and Well Technology book. He holds 15 patents within intelligent well technology. Maurice B Dusseault, PhD, PEng, is a Professor of Geological Engineering at the University of Waterloo, Waterloo, Ontario in the Department of Earth and Environmental Sciences. With strong ties to industry, he pursues subsurface engineering, geophysics and geomechanics issues in the energy and mining sectors. His experience includes oil and gas development, deep slurried granular waste and biosolids injection, CO2 sequestration, energy storage (compressed air, H2/CH4, or heat), geothermal energy, thermohydromechanical coupling in rock masses, and many related subjects. His research and academic product exceeds 625 published papers in Journals and good quality Conferences, as well as two textbooks co-authored with Dr J.A. Franklin. He holds many patents, has supervised over 100 graduate students, and has generated six technically-oriented start up companies in his career. ii Contents Chapter 1: Deep Well Scenario ............................................................................................................... 1 1.1 Introduction to Deep Well Scenario ............................................................................................. 1 1.2 Review of Construction of Deep HPHT Wells ............................................................................... 1 1.2.1 Time and Cost of a Deep Petroleum Well ............................................................................. 6 1.3 Plugging and Abandonment of Deep Oil Wells ............................................................................. 7 1.4 Oil Well Reference to Deep Repository Well .............................................................................. 11 1.5 Shallower Onshore Oil Well as a Reference................................................................................ 13 1.6 Multiple Downhole Branches ...................................................................................................... 14 1.7 Summary ..................................................................................................................................... 15 Chapter 2: Land Wells and Boreholes in Crystalline Rock .................................................................... 17 2.1 Overview of Wells and Boreholes in Crystalline Rock ................................................................ 17 2.2 Scientific Exploration Boreholes ................................................................................................. 18 2.2.1 Kola Superdeep Borehole ................................................................................................... 19 2.2.2 KTB ...................................................................................................................................... 20 2.2.3 San Andreas Fault Zone Observatory at Depth (SAFOD) .................................................... 22 2.2.4 Chinese Continental Scientific Drilling (CCSD) .................................................................... 23 2.3 Geothermal Wells ....................................................................................................................... 25 2.3.1 EGS Projects in Finland ........................................................................................................ 26 2.3.2 Soultz-sous-Forêts ............................................................................................................... 27 2.3.3 Basel-1 ................................................................................................................................. 27 2.3.4 Icelandic Deep Drilling Program (IDDP) .............................................................................. 29 2.4 Comparison of Oilfield and Mining Drilling ................................................................................. 30 2.5 Mining Industry Drilling in Crystalline Rock ................................................................................ 31 2.6 Considerations for Deep Well Engineering in Crystalline Rock................................................... 34 2.7 Summary ..................................................................................................................................... 38 Chapter 3: Well Plugging ....................................................................................................................... 40 3.1 Introduction to Well Plugging ....................................................................................................