Marriott has recently completed a long-term contract in Switzerland on behalf of NAGRA, the Swiss federal agency investigating the safe and responsible disposal of radioactive waste from industry. The aim of the drilling campaign was to characterise the subsurface of three potential siting regions located at the edge of the Northern Alpine Molasse Basin. For site selection and the development of a safety case for a deep geological repository, Marriott were contracted to provide the drilling and coring services on a fully integrated basis. This included the supply of all casing, bits, drilling fluids and well materials in addition to the cementing, drill fluid engineering and waste disposal services to construct the wells and enable the extensive testing and logging programmes to take place.
Between 2019 and 2021, Marriott was contracted to drill four wells ranging in depth from 850 m to 1,350 m and totalling 5,338 m drilled over the campaign, with one including a 35o deviated section. Due to the scientific nature of this drilling campaign NAGRA required high-quality core recovery and good quality wellbore for long subsurface testing phases. In terms of coring, Marriott delivered 100% core recovery with a total of 2650 m of core in various rock formations. The quality of the boreholes themselves also enabled close to 100% log coverage over the potential host rock formations. Testament to Marriott’s commitment to high HSEQ standards and performance, the entire work programme was delivered as per schedule with zero lost time incidents recorded.