How facies and diagenesis affect fracturing of limestone beds and reservoir permeability in limestone–marl alternations

摘要: Abstract Facies and diagenetic heterogeneities in carbonate reservoir rocks affect both, fracture distribution permeability. Many studies focussed on patterns limestone–marl alternations, as e.g. fluid flow models, are based laterally continuous beds. Here we examine 4010 fractures multiple layers of alternations using a modified scan-line method. The studied successions belong to the Blue Lias Formation (Hettangian–Sinemurian), exposed coast Bristol Channel, United Kingdom. We combine methods sedimentology structural geology with rock physics gain better understanding role facies, diagenesis petrophysical properties (tensile compressive strength, hardness, porosity) (fracture orientation, density, spacing height). Fracture varies significantly despite similar bed thicknesses, indicating that planar bedding planes (i.e. well-bedded limestones, WBL) beds plane irregularities semi-nodular SNL) must be distinguished. SNL show higher percentages non-stratabound (67%) while they more stratabound WBL (57%). Additionally, variable thicknesses (in scale 15 m long beds) exhibit wide range spacing, whereas regularly spaced. Considering all lithologies, percentage increases proportionally CaCO 3 content. Three subsections detail reveal different main sedimentological features (from early lithified over differentially compacted physically compacted). All them characterised by dissimilar limestone marl interbeds. Our findings demonstrate individual limestones is not necessarily representative for alternations; should therefore outcrop analogues basis models reservoirs composed such lithologies.