Source rocks in foreland basins: A preferential context for the development of natural hydraulic fractures

Abstract

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 this review, we demonstrate that beef veins are most commonly present in foreland basins worldwide or in basins 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 of compressive stress activity. This is especially the case for the Wessex Basin (UK) and the Neuquén Basin (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 vein formation 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 of fracturing demonstrate that bedding-parallel fractures can be generated only with a distributed fluid overpressure, the formation of beef veins seems to be a consequence of both fluid overpressures and a compressional tectonic stress.

Trace fossils as mechanical discontinuities in shales, insight for the generation of bedding-parallel veins (BPV)

“…3A-E; B-F). During stage (3), in addition to these radial patterns (Fig. 3D-H), the local stress field promotes the development of the BPV with a tongue-shaped morphology whose major axis is aligned with the main stress (NNE-SSW) 19 (Fig.…”

“…Bedding-parallel fibrous veins (BPV) are very common worldwide in sedimentary basins on Earth, especially within or near shales 1 – 3 as well as in lacustrine rocks on Mars 4 . The origins of BVP generation is still debated.…”

“…The origins of BVP generation is still debated. While there is consensus about the involved parameters, such as the fluid overpressure buildup 5 , the maturation of organic matter and fossils 6 , 7 , the force of crystallization 8 , 9 , and the tectonic stresses 3 , 10 , there is no evidence in favor of one parameter being more important than the others. On the other hand, it is well known that sedimentological parameters, such as bioturbation, change the primary petrophysical characteristics (i.e.…”

Genesis of Fibrous Calcite in the Chang 7 Member of the Yanchang Formation, Ordos Basin, China

“…The initial opening of the antitaxial fibrous vein is considered to be the result of hydrofracturing due to excess fluid pressure (Zhao and Li, 2022). Zanella et al (2021) argued that the formation of beef veins may also need to be facilitated by a compressional tectonic stress inducing rock fracturing. Excess fluid pressure is mainly caused by hydrocarbon generation, tectonic compression and mineral transformation (Zhao and Li, 2022).…”