'Good practice' guide for lessons learned from deep geothermal drilling - Final report

On 19 December 2014 (Lessons learned from Deep Drilling Phase 1 project) and 26 October 2016 (Lessons learned from Deep Drilling Phase 2 project), BRGM was commissioned to produce a 'good practice' guide for deep geothermal drilling in the Ile-de-France region, on behalf of the Comite Technique Geothermie sur Aquiferes Profonds (CT-GAP - Technical Committee on Deep Aquifer Geothermal Energy), which brings together the organisations involved in the development of deep aquifer geothermal energy (ADEME, AFPG, AGEMO, BRGM, DRIEE, SAF-Environnement, SNCU). The purpose of this guide is to provide project owners and project managers with recommendations when carrying out deep geothermal drilling. It is based on lessons learned from the drilling carried out in the Dogger and Albian/Neocomian aquifers, as well as from the rehabilitation work carried out since the resumption of geothermal drilling in the Paris Basin in 2007. The guide was based on the analysis of 36 operations carried out between 2007 and 2018 in the Ile-de-France region, representing a total of 65 boreholes, including 55 targeting the Dogger aquifer, 8 the Albian aquifer and 2 the Neocomian aquifer. Initially, 19 fact sheets were drawn up at the end of 2017 and, between 2018 and 2019, four new fact sheets were produced, including one rewrite of an existing fact sheet. This drilling work or, in some cases, renovation work has allowed significant lessons to be learned on the best techniques or principles to be used to avoid malfunctions or incidents that could jeopardise the sustainability of operations. New techniques and materials have also been used. Over the last twelve years, the number of geothermal operations has thus gradually increased in the Ile-de-France region, allowing the accumulation of a significant amount of information and experience, sometimes positive and worthy of being leveraged as best practices and sometimes negative, either immediately or in the medium term, and for which the fact sheets presented propose possibilities for correction or improvement as well as recommendations. The idea is not to make deep geothermal well construction principles mandatory or normative but rather to provide a reminder of the main best practices to be followed. Finally, the aim is to provide, wherever possible, indicators to appraise or assess the quality of the work carried out. This guide currently includes 22 fact sheets divided into 9 categories (Reminders of best practices and surface area, Drilling, Casings, Cementing, Deviation, Completion, Loggings, Development and testing, Operation). The complete version of the guide and each individual fact sheet can be consulted and downloaded from the geothermal energy prospects web site http://www.geothermie-perspectives.fr/document/guide-bonne-pratique-dun-foragegeothermique-en-aquifere-profond-en-ile-france