Source rocks in foreland basins: a preferential context for the development of natural hydraulic fractures
Résumé
Bedding-parallel veins of fibrous calcite (also called BPV or ‘beef’) occur in many sedimentary basins, especially those containing low-permeability strata with organic source material for petroleum.The formation of such veins is often linked with fluid overpressure in these source rocks. In thisreview, we demonstrate that beef veins are most commonly present in foreland basins worldwide or inbasins that recorded a compressive tectonic period. The formation of beef veins is related to two main phases: (1) the initiation of bedding-parallel fracture and (2) the infilling of the fracture.Previous structural studies have shown that formation of beef veins occurred during a period ofcompressive stress activity. This is especially the case for the Wessex Basin (UK) and the NeuquénBasin (Argentina). Here we provide more observations for other basins: the Cordillera Oriental(Colombia), the Paris Basin (France), the northern Pyrenees (France), the Uinta Basin (US), the Tian Shan Mountains (central Asia) and the Appalachian Mountains (US). In the Paris Basin, beef veinformation is dated at 155 Ma (U/Pb calcite method) and is coeval with the compressional deformation in the eastern part of the basin.Because of the timing of generation for such veins and even if the theory and the experiments offracturing demonstrate that bedding-parallel fractures can be generated only with a distributed fluidoverpressure, the formation of beef veins seems to be a consequence of both fluid overpressures and acompressional tectonic stress.
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