Mahmoud Hefny Publications

Mahmoud Hefny

PhD Student for Geothermal Energy and Geofluids


Mailing Address
Mahmoud Hefny
Geothermal Energy & Geofluids
Institute of Geophysics
NO FO 47.2
Sonneggstrasse 5
CH-8092 Zurich Switzerland

Phone +41 44 632 6538
Email mhefny(at)

Dominique Ballarin Dolfin
Phone +41 44 632 3465
Email ballarin(at)


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Hefny, M., A. Zappone, Y. Makhloufi, A. de Haller, and A. Moscariello A laboratory approach for the calibration of seismic data in the western part of the Swiss Molasse Basin: the case history of well Humilly-2 (France) in the Geneva area Swiss Journal of Geosciences , 113/11, 2020. [Download PDF] [View Abstract]A collection of 81 plugs were obtained from the Humilly-2 borehole (France), that reached the Permo-Carboniferous sediments at a depth of 3051 m. Experimental measurements of physical parameters and mineralogical analysis were performed to explore the links between sedimentary facies and seismic characteristics and provide a key tool in the interpretation of seismic field data in terms of geological formations. The plugs, cylinders of 22.5 mm in diameter and ~30 mm in length were collected parallel and perpendicular to the bedding in order to explore their anisotropy. Ultrasound wave propagation was measured at increasing confining pressure conditions up to 260 MPa, a pressure where all micro-fractures are considered closed. The derivatives of velocities with pressure were established, allowing the simulation of lithological transitions at in-situ conditions. At room conditions, measured grain densities [kg/m3] range from 2630 to 2948 and velocities vary from 4339 to 6771 m/s and 2460 to 3975m/s for P- and S-waves propagation modes, respectively. The largest seismic-reflections coefficients were calculated for the interface between the evaporitic facies of the Keuper (Lettenkohle) and the underlying Muschelkalk carbonates (Rc= 0.3). The effective porosity has a range of 0.23% to 16.65%, while the maximum fluid permeability [m2] is 9.1e-16. A positive correlation between porosity and ultrasound velocity has been observed for P- and S-waves. The link between velocities and modal content of quartz, dolomite, calcite, and micas has been explored. This paper presents a unique set of seismic parameters potentially useful for the calibration of seismic data in the Geneva Molasse Basin.

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Hefny, M., C.-Z. Qin, A. Ebigbo, J. Gostick, M.O. Saar, and M. Hammed CO2-Brine flow in Nubian Sandstone (Egypt): Pore-Network Modeling using Computerized Tomography Imaging , European Geothermal Congress (EGC), 2019. [View Abstract]The injection of CO2 into the highly permeable Nubian Sandstone of a depleted oil field in the central Gulf of Suez Basin (Egypt) is an effective way to extract enthalpy from deep sedimentary basins while sequestering CO2, forming a so-called CO2-Plume Geothermal (CPG) system. Subsurface flow models require constitutive relationships, including relative permeability and capillary pressure curves, to determine the CO2-plume migration at a representative geological scale. Based on the fluid-displacement mechanisms, quasi-static pore-network modeling has been used to simulate the equilibrium positions of fluid-fluid interfaces, and thus determine the capillary pressure and relative permeability curves. 3D images with a voxel size of 650 nm3 of a Nubian Sandstone rock sample have been obtained using Synchrotron Radiation X-ray Tomographic Microscopy. From the images, topological properties of pores/throats were constructed. Using a pore-network model, we performed a cycle of primary drainage of quasi-static invasion to quantify the saturation of scCO2 at the point of a breakthrough with emphasis on the relative permeability–saturation relationship. We compare the quasi-static flow simulation results from the pore-network model with experimental observations. It shows that the Pc-Sw curve is very similar to those observed experimentally.