Study of electrical properties and petrography for carbonate rocks in the Jurassic Formations: Sinai Peninsula, Egypt
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ORIGINAL PAPER
Study of electrical properties and petrography for carbonate rocks in the Jurassic Formations: Sinai Peninsula, Egypt Mohamed M. Gomaa & Mohamed A. Kassab & Nahla A. El–Sayed
Received: 7 May 2014 / Accepted: 4 July 2014 # Saudi Society for Geosciences 2014
Abstract Electrical methods are used in a wide range of applications including groundwater, geothermal, mineral discovery, oil and gas exploration, and deep tectonic processes. The Jurassic sedimentary section in North Sinai is of a special interest in particular for its economic potentiality and environmental conditions such as continental, marine, fluviomarine. The understanding petrographical and electrical properties of these rocks are essential for investigating minerals, oil, and water exploration. This paper presents a study of the petrographical and AC electrical properties of the Jurassic carbonates. Electrical measurements have been conducted for twenty nine (29) carbonate samples. The slight changes between samples in electrical properties were attributed to the changes in mineral composition, texture pore spaces, and pore throat distribution of the samples. Electrical properties generally change with many factors (grain size, mineral composition, grain shape, and facies). The dielectric constant decreases with frequency and increases with the presence of conductive solids (silt and clay) and its composition. The conductivity increases with the increase of conductor paths between electrodes. The main goal of this paper is to shed more light on interrelations between electrical properties (conductivity, dielectric constant and impedance as a function of frequency), petrography, and mineral composition (carbonates that contain clays and quartz grains). This is the first time to make some complex electrical properties on the carbonate rocks at this area as a prelude to make forward and inverse modeling.
M. M. Gomaa (*) Geophysical Sciences Department, National Research Center, Cairo, Egypt e-mail: [email protected] M. A. Kassab : N. A. El–Sayed Exploration Department Egyptian Petroleum Research Institute, 11727 Cairo, Egypt
Keywords Conductivity . Dielectric constant . Frequency domain . Jurassic . Carbonate rocks
Introduction and geologic setting Sinai Peninsula lies at the northeast of Egypt (Fig. 1). North Sinai is considered shallow shelf areas with low relief during Jurassic period. The complete section of Jurassic rocks is exposed at Gebel El-Maghara area (Fig. 2), between longitudes 33 ° 18′–33 ° 27′ E. and latitudes 30 ° 38′–30 ° 44′ N (Jenkins et al. 1982, Abd El Aal and Lelek 1994). (1966) subdivided the strata below El-Maghara area into six alternative continental and marine formations having a total thickness of about 1,900 m. These formations are arranged from top to bottom as follows: Masajid Formation, Safa Formation, Bir Maghara Formation, Shusha Formation, Rajabia Formation, and Mashaba Formation. The dominant rocks are limestones and dolomites. The following items are related to carbonates: marl (about 50 % carbona
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