The coal cleat system: A new approach to its study

Abstract

After a general analysis regarding the concept of coal “cleat system!”, its genetic origin and practical application in Coalbed methane (CBM) commercial production and in CO2 geological sequestration projects, the authors have developed a method to answer, quickly and accurately according with the industrial practice and needs, to the following yet unanswered questions: (i) how to define the spatial orientation of the different classes of cleats present in a coal seam, and (ii) how to determine the frequency of their connectivites? The new available and presented techniques to answer these questions have a strong computer based tool (Geographic Information System (GIS)), able to build a complete georeferentiated database, which will allow to three-dimensionally locate the laboratory samples in the coalfield. It will also allow to better understand the coal cleat system and consequently to recognise the best pathways to gas flow through the coal seam. Such knowledge is considered crucial for understanding what is likely to be the most efficient opening of cleat network, then allowing the injection with the right spatial orientation, of pressurized fluids or propants in order to directly drain the maximum amount of gas flow to a CBM exploitation well. The method is also applicable to the CO2 Geological Sequestration Technologies, operations corresponding to the injection of CO2 sequestered from industrial plants in coal seams of abandoned coalmines or high depth coal seams.