The Uses of The Al-Faidiyah Formation Oligocene-Miocene in The Drilling Mud Fluids (Bentonite) at Umm Ar Razam, North-East Libya

Abstract

The lower member (Faidia Clay) of the Oligocene-Miocene Al Faidiyah Formation at Umm Ar Razam Quarry, northeast Libya has been investigated for its potential as a chemical additive (bentonite) in drilling oil wells. The thickness in outcrop of the examined clay unit is variable but information from the subsurface indicates a maximum thickness of about 25 m. Normally, these clay deposits have a dark green color that becomes brown when weathered. When wet, the clay forms a very plastic sticky mass with soap-like textures. A number of mineralogical, chemical, and physicochemical laboratory analyses using X-ray diffraction (XRD), scanning electron microscopy (SEM-SE & SEM-BSE), X-ray fluorescence (XRF), ion exchange capacity (CEC) and surface area have been made in order to characterize the grade and quality of the examined clays. The overall results show that montmorillonite represents the highest percentage (46 %), minor kaolinite (36 %), and trace chlorite (4 %). Other minerals of heterogeneous mixtures of non-clay minerals such as fine quartz grains, calcite, dolomite, gypsum, K-feldspar, ilmenite, anatase, and hematite are also recognized. The presence of a heterogeneous mixture of non-clay minerals reduces the rheological and physical properties as well as detracts from the commercial performance of the Faidia clay. The unprocessed clay and clay after treatment with the addition of up to 6 % of Na₂CO₃, did not achieve a swelling volume comparable with standard bentonite. The Faidia Limestone Member (the upper part of the Al Faidiyah Formation) is characterized by very high purity in Al Fatayah Quarry. It is extensively used for concrete aggregates, road tiles, blocks, paints, carpets, the cement industry, papers, pharmaceuticals, water treatment, agriculture, and plastics. The equivalent member in Umm Ar Razam Quarry has a lower grade due to the presence of other carbonates (dolomite) and non-carbonates such as quartz, clay, and glauconite minerals. Fossil contents and lithological nature indicate that this is a typical shelf environment.