CHEMICAL COMPOSITION OF THE MINERAL MATTER OF THE ATTARAT UM GHUDRAN OIL SHALE, CENTRAL JORDAN

Abstract

The concession area of the Jordan Oil Shale Energy Co (JOSE) is located in the southern border zone of the Attarat Um Ghudran deposit, next to the Wadi Maghara deposit, both consisting of marinite type oil shale (OS). These deposits of the Upper Cretaceous to Lower Paleogene Muwaqqar Chalk-Marl Formation form a huge north-southward elongated oil shale basin in Central Jordan, with resources over 55 billion tons. JOSE has drilled a regular grid of boreholes with a full coring of the up to 90 m thick OS seam and its lower and upper contact layers. Visually, the OS unit is a rather homogenous dark-colored (grey, black, brownish grey) succession of finely bedded (laminated) kerogen-bearing carbonate rocks that has been in earlier papers described as a uniform lithological unit. The aim of the geological and lithological studies of the JOSE exploration area was (i) to investigate the vertical variation of OS composition and, if present, to define layers within the OS unit, and (ii) to identify lithological varieties and chemical composition of OS present in different layers. On the basis of field evidence, downhole gamma-logging, chemical analyses and other criteria, an original detailed scheme of the layered structure of oil shale and barren rocks was introduced. A total of eight OS layers (indexed as A, B1, B2, C, D, E1, E2, E3) and at least four barren dolomitic limestone interlayers were distinguished. The present publication is dedicated to the chemical study of the layers and the total OS seam. A representative gapless collection of 632 conventional core samples from 12 cores serves as the base for the comparative study of the layers. Two main (SiO2, CaO) and two subordinate chemical (Al2O3 and P2O5) components of the mineral matter (MM), and loss on ignition (LOI 500 °C) approximately reflecting the content of organic matter (OM), are the basic variables dis- cussed. Contents of SiO2 and CaO always show negative correlation,