Characteristics of secondary fracture systems in coal mines and their potential application in mine water geothermal systems

May 17, 2023 | Lecture Archive

Jerome Amory (PanTerra)

Abandoned coal mines represent a very-low enthalpy resource base that is typically located in the direct proximity of former industrial urban areas where the population density is high. This creates a logical fit between a geothermal resource that has an established enhanced permeability system (the coal mine) and a local and dense heat demand at surface that can be connected to a district heating (and cooling) distribution system.
Few of the existing mine water systems have used wells to target the mine resource at depth. Where wells are used, they typically target galleries to guarantee a high production and injection rate. The interconnection of the galleries does ensure that the system works as a closed loop. However, this direct connectivity also comes with a significant risk of early thermal breakthrough.
Aside from the constructed infrastructure system of galleries and shafts that have an extremely high permeability and good connectivity, the mine system also has a very extensive network of enhanced permeability that has developed around the excavation zones with the development of collapse structures.
In mechanized longwall mining operations these collapse structures (called “goaf” or “gob”) develop above the coal seam when the roof collapses behind the cut face and its supporting (and advancing) heavy machinery. These induced fracture networks are laterally and vertically extensive and they have predictable geometries. Targeting this fracture system would provide a more tortuous flow path that increases the thermal exchange capacity with the host rock and reduces the risk of accelerated thermal breakthrough between injector and producer.
This talk has three parts. First, a brief overview of mine water geothermal systems, with some examples. Second, an explanation of longwall mining operations and how these generate a predictable fracture system in the surrounding strata. Third, some conceptual suggestions to integrate these induced fractured systems into the development of mine water geothermal systems.

About the presenter
Jerome Amory is a geologist with over two decades of international exposure delivering integrated O&G energy projects across the full resource exploration and development lifecycle. He is now leveraging this experience to support the energy transition, with focus on deep geothermal energy systems.
Jerome graduated with an M.Sc. from Stanford University and worked for 24 years with Shell International. He has been the Chief Geologist and Renewable Energy lead at PanTerra since 2022.


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PGK lecture 17-05-2023 Jerome Amory (PanTerra) Characteristics of secondary fracture systems in coal mines and their potential application in mine water geothermal systems

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