Micro- to macro-scale internal structures, diagenesis and petrophysical evolution of injectite networks in the Vocontian Basin (France): Implications for fluid flow

This study discusses the characteristics of two Lower Cretaceous injectite networks in the Vocontian Basin (SE France) using combined structural, sedimentary, diagenetic, and petrophysical analyses. Internal structures, at both the macro- and micro-scale, and diagenetic phases characterising these injectite networks have been described. Simultaneously, precementation porosity values were estimated and parameters controlling the geographical distributions of these values were analysed and statistically tested. All of the data were integrated so as to reconstruct the spatial evolution of the porosity from the time of injection to modern times through five major phases. (1) The injection of fluidised sand into hydrofractures combined with high porewater pressure results in high porosity (up to 53%) where injectite thickness and distance to the parent beds exert a primary control. (2) Early deformational imprints, including elutriation structures and cataclastic deformation bands, cause a reduction in the localised porosity. (3) At low burial depths, the intruded sand becomes pervasively cemented by carbonate and is associated with a drastic decrease in porosity (