Petrophysical Properties and Microstructural Analysis of Faulted Heterolithic Packages: A Case Study from Miocene Turbidite Successions, Italy

Abstract

Geofluid reservoirs located in heterolithic successions (e.g., turbidites) can be affected by vertical and lateral compartmentalization due to interbedded fine-grained facies (i.e., shale, siltstones) and the presence of faults, respectively. A fault can behave as a conduit or barrier to fluid flow depending on its architecture and the individual hydraulic behavior of its components (i.e., fault core, damage zone). The fault core, normally composed by fault rock or smeared clay material, commonly acts as a flow inhibitor across the fault. Fault-related fractures (macro- and microscopic) in the damage zone generally increase the permeability parallel to the fault, except when they are cemented or filled with gouge material. Although macrofractures (which define the fracture porosity) dominate fluid flow, the matrix porosity (including microfractures) begins to have a more important role in fluid flow as the aperture of macrofractures is occluded, particularly at greater depth. This study investigates the variation in matrix permeability in fault zones hosted in heterolithic successions due to fault architecture and stratigraphy of host rock (i.e., sand-rich turbidites). Two key areas of well-exposed, faulted Miocene turbidites located in central and southern Italy were selected. For this study, six separate fault zones of varying offset were chosen. Each impacts heterolithic successions that formed under similar tectonic conditions and burial depths. Across the selected fault zones, an extensive petrophysical analysis was done in the field and laboratory, through air permeameter measurements, thin section, and synchrotron analysis in both host rock, damage zone, and fault core. Results suggest that the amount and distribution of clay layers in a heterolithic sequence affects fluid flow across the fault, regardless of fault offset.

Mineralogical characteristics of the heterolithic formations from the Carpathian Foredeep Miocene sediments, south-eastern Poland

“…Many publications are focused mainly on methods of permeability calculations in heterolithic formation profiles (e.g., Norris & Lewis 1991, Jackson et al 2003, Nordahl & Ringrose 2008, but really the most important problem in heterogeneous reservoir studies is integrating data from different samples, acquired using different test methods (Enderlin et al 1991, Worthington 1994, Gupta et al 1996, Corbett et al 1998, Martinius et al 2005. A reliable reconstruction of the reservoir properties distribution is possible only on the basis of fully integrated data (Nordahl 2004, Riegel et al 2019.…”

“…Ms and Cs from the P zone display high swelling capacity (CEC over 20 meq/100g). Przelaskowska A., Zagórska U., Urbaniec A., Łykowska G., Klaja J., Grela J., Kędracka It should be emphasized that lithofacial classifications of heterolithic formations are usually based on sedimentological studies, macroscopic and microscope observations (Donselaar & Geel 2007, Siddiqui et al 2017, Riegel et al 2019). The presented work was aimed at using macroscopic observations as well as XRD and XRF studies for distinction and characterization of particular lithotypes.…”

Determination of Petrophysical Properties Cutoff in Heterolithic Reservoirs in Malay Basin

“…Log readings of the sandstone laminae are commonly suppressed by shoulder effects [16] and sometimes are not resolved at all [17,18]. Vertical and lateral compartmentalisation due to stratigraphic complexities or small faults is common [19]. Finally, heterolithic sandstone reservoirs usually suffer from relatively low recovery factors, less than 30% [20].…”

Shear Behavior and Anisotropy Characteristics of the Fracture Morphology of Sandstone with Different Water Contents

“…Hydromechanical coupling in rock masses is an important issue for many rock mechanics and hydrogeology applications [1][2][3][4][5][6][7]. In mining and civil engineering, the redistribution of the stress field during the excavation of tunnels and underground caverns leads to the initiation and propagation of cracks, which can cause dramatic changes in the permeability of a rock mass [8,9].…”