Effect of normal fault activity on carbonate reservoir diagenetic evolution (Urgonian facies, SE France)

Abstract

<h3>Normal fault zones can have a significant role on fluid flows as they can form barriers or drains (Agosta et al., 2010; Bense et al., 2013; Brogi and Novellino, 2015). In carbonates rocks, which are very sensitive to fluid-rock interactions, these fault-related fluid flows can strongly enhance or alter carbonate reservoir properties (Deville de Periere et al., 2017; Fournier and Borgomano, 2009).</h3><h3>This work aims at determine fluid flow evolution in a carbonate reservoir affected by a normal fault. For this purpose, we studied structural and diagenetic properties of the Esperelles normal fault and the surrounding Barremian and Aptian formations located on the northern flank of Nerthe anticline (SE France). Esperelles fault developed during the Durancian uplift (Albian) and was weakly reactivated during the opening of Liguro-Provençal basin during Oligo-Miocene times.</h3><h3>We defined seven different cements under cathodoluminescence (C0 to C6), their distributions along the outcrop, their geochemical properties (<sup>18</sup>O and <sup>13</sup>C stable isotopes, Δ<sub>47</sub> thermometry), and their ages (U-Pb). Diagenetic properties have been correlated with petrophysical measurements. We determined the paragenetic sequence, as well as the nature and temperature of the fluids that led to the formation of C1 and C6 cements. Four U-Pb ages have been obtained using an ELEMENT XR (Thermo-Fisher) SF-ICP-MS coupled to a 193 nm Excimer Laser (ESI) at CEREGE (Aix-en-Provence, France).  These ages allowed to relate the C6 cementing phase with the opening of Liguro-Provençal basin. This study shows that fault zone development impacted reservoir fluid flows, leading to significant diagenetic events and development of heterogeneous reservoir properties.</h3><p> </p><h3><em><strong>References</strong></em></h3><p>Agosta, F., Alessandroni, M., Antonellini, M., Tondi, E. and Giorgioni, M.: From fractures to flow: A field-based quantitative analysis of an outcropping carbonate reservoir, Tectonophysics, 490(3–4), 197–213, doi:10.1016/j.tecto.2010.05.005, 2010.</p><p>Bense, V. F., Gleeson, T., Loveless, S. E., Bour, O. and Scibek, J.: Fault zone hydrogeology, Earth-Science Rev., 127, 171–192, doi:10.1016/j.earscirev.2013.09.008, 2013.</p><p>Brogi, A. and Novellino, R.: Low Angle Normal Fault (LANF)-zone architecture and permeability features in bedded carbonate from inner Northern Apennines (Rapolano Terme, Central Italy), Tectonophysics, 638(1), 126–146, doi:10.1016/j.tecto.2014.11.005, 2015.</p><p>Deville de Periere, M., Durlet, C., Vennin, E., Caline, B., Boichard, R. and Meyer, A.: Influence of a major exposure surface on the development of microporous micritic limestones - Example of the Upper Mishrif Formation (Cenomanian) of the Middle East, Sediment. Geol., 353, 96–113, doi:10.1016/j.sedgeo.2017.03.005, 2017.</p><p>Fournier, F. and Borgomano, J.: Critical porosity and elastic properties of microporous mixed carbonate-siliciclastic rocks, Geophysics, 74(2), E93–E109, doi:10.1190/1.3043727, 2009.</p>