Diagenetic evolution of fault zones in Urgonian microporous carbonates, impact on reservoir properties (Provence – southeast France)

Abstract

<jats:p>Abstract. Microporous carbonate rocks form important reservoirs with permeability variability depending on sedimentary, structural, and diagenetic factors. Carbonates are very sensitive to fluid–rock interactions that lead to secondary diagenetic processes like cementation and dissolution capable of modifying the reservoir properties. Focusing on fault-related diagenesis, the aim of this study is to identify the impact of the fault zone on reservoir quality. This contribution focuses on two fault zones east of La Fare anticline (SE France) crosscutting Urgonian microporous carbonates. Overall, 122 collected samples along four transects orthogonal to fault strike were analyzed. Porosity values have been measured on 92 dry plugs. Diagenetic elements were determined through the observation of 92 thin sections using polarized light microscopy, cathodoluminescence, carbonate staining, SEM, and stable isotopic measurements (δ13C and δ18O). Eight different calcite cementation stages and two micrite micro-fabrics were identified. As a main result, this study highlights that the two fault zones acted as drains canalizing low-temperature fluids at their onset and induced calcite cementation, which strongly altered and modified the local reservoir properties. </jats:p>

Evidence of kilometer-wide shallow bulk plastic yielding along the 2021 Maduo, Tibet, surface rupture, and its relation with the dynamic rupture process

“…Such increase in ∇d ̅̅̅̅ in the localized deformation regions do not lead to significant changes in the FZW, showing the ability of the localized deformation to concentrate large amounts of deformation within confined regions, hence representing a highly energy-efficient deformation regime. Such comparison between a natural rupture and crystalline rock samples being deformed in the laboratory, is also supported by other deformation experiments in granular porous medium (Aben et al, 2017;Baud et al, 2000;Cilona et al, 2012;Fossen et al, 2007;Visage et al, 2023), as well as field observations (Aubert et al, 2020;Cilona et al, 2012;Micarelli et al, 2006), strengthening our previous interpretations. In the case of the 2021 Maduo rupture, indeed, lithology consists in granular porous carbonate rocks overlaid with unconsolidated quaternary sediments at some locations (Ren et al, 2021;Yuan et al, 2022), which differ from the crystalline nature of the rock used in the experiments described previously.…”

“…Added to the lowpressure conditions of the shallow crust and interactions with the free-surface, plastic deformation processes can differ from that described previously. In this case, shear and/or dilatation deformation bands (Aben et al, 2017;Aubert et al, 2020;Fossen et al, 2007;Micarelli et al, 2006;Visage et al, 2023), and possibly viscous cataclastic flow (Baud et al, 2000;Cilona et al, 2012) have been suggested as the primarily plastic deformation mechanisms, in addition to the microfracturing occurring in the most consolidated, e.g., cemented and/or healed, regions (Micarelli et al, 2006).…”

Structural diagenesis of deep carbonate rocks controlled by intra‐cratonic strike‐slip faulting: An example in the Shunbei area of the Tarim Basin, NW China

“…Typically, fault zones form as a result of the accumulation of multiple slip events (Schlische et al, 1996). As the slip magnitude increases, fractures become more numerous and may be defined by wide damage halos (Aubert et al, 2020). According to previous studies of high‐resolution 3D seismic data, the SB5 fault zone is a major fault zone that cuts across the Tabei, Shuntuoguole Low, and Tazhong uplifts, and its scale and intensity are substantially larger than those of the SB1 fault zone (Deng, Li, Han, et al, 2019;Lin et al, 2021; Yun, 2021).…”

How the geochemistry of syn-kinematic calcite cement depicts past fluid flow and assists structural interpretations: a review of concepts and applications in orogenic forelands

“…Of course, it is mandatory to have the best understanding of the diagenesis history of a fracture-filling cement to be sure of what is actually dated, especially in fault zones where numerous dissolution-precipitation, recrystallization and/or successive fluid flow events can be recorded (e.g. Aubert et al 2020). That being done, it becomes possible to date not only the timing of deformation, but also the duration of some events.…”