3D geological modelling from boreholes, cross-sections and geological maps, application over former natural gas storages in coal mines

In a wide range of applications involving geological modelling, geological data available at low cost usually consist of documents such as cross-sections or geological maps and punctual data like borehole logs or outcrop descriptions.In order to build accurate 3D geological models based on this information, it is necessary to develop a methodology that takes into account the variety of available data. Such models, of the geometry of geological bodies, should also be easy to edit and update to integrate new data. This kind of model should produce a consistent representation of subsurface geology that may be a support for modelling other subsoil characteristics such as hydrogeologic or geothermic properties of the geological bodies.This paper presents a methodology developed to process geological information in this context. The aims of this methodology are comprehensive data description, effective data validation and easier model updates. Thus, special attention has been given to data structures and processing flows. The adopted methodology is implemented on a system architecture formed by a geographic information system, a geomodeler and a database communicating by file transfers.An application of this methodology, to build a 3D geological model of the subsoil over former coalmines used to store natural gas, is then presented. This model integrates the geological information available and is representative of the geological context. It is a support to the environmental follow-up needed after the end of gas-storage operations.