oa Mineralogy and Illite/Smectite Mixed-Layer Expandability of Rudies Formation and Its Relation to Maturation of Organic Matter, in the Southern Sector of the Gulf of Suez, Egypt

The X-ray diffraction analysis of 29 bulk samples and 21 clay fractions samples derived from Rudies<br>Formation, that present in Gabal El-Zeit and Morgan basins in the southern part of the Gulf of Suez,<br>are used to define the mineralogic composition of this formation. This rock unit is composed mainly of<br>quartz, dolomite and calcite associated with minor amounts of phyllosilicates, such as kaolinite and<br>illite/smectite mixed-layer, as well as traces of K and Na feldspars, and hematite. The analysis of clay<br>fraction of the studied samples indicated that, illite/smectite mixed-layer is the main mineral<br>component in Gabal El-Zeit Basin, followed by kaolinite, in which kaolinite is the main clay mineral,<br>followed by illite/smectite mixed-layer in El-Morgan basin. Illitization of illite/smectite mixed-layer is<br>the main process in this study, which indicated that the random interstratification (R=0) of<br>illite/smectite mixed-layer is present in two stages of organic matter maturation at Gabal El-Zeit Basin<br>smectite percentage (S%) ranges between 85 and 80%, present in temperature range from 28 to 46 °<br>C indicating immature stage. whereas random interstratification in Morgan basin are situated in with<br>smectite percentage ranged between 60 and 50 and temperature range 90 to 91°C, reflects mature source rock.<br>The ordered interstratification (R=l) has S% ranged between 40 and 25 % present at depth range from<br>2413 to 3055m and temperature range 94 to 103°C is also detected. While (R=3) illitization stage is<br>identified with S% ranged between 15 and 10 %, is present at depths 3250 and 3480m and have<br>temperature range of 115-137 °C which reflecting end of oil generation stage, whereas R≥3 illitization<br>stage with S% of 10% or less is present at depth ranged from 3445 to 3550m and temperature from<br>139 to 143°C which indicating wet gas stage. Generally, these illitization stages and temperature<br>ranges show that, the organic matter content of Rudeis Formation at Gabal El-Zeit Basin is present in<br>immature stage, whereas the organic matter in Rudeis Formation at Morgan basin is attending in a<br>range of oil window and wet gas stage.