The upper Triassic sandstone reservoir (Mulussa F formation) is a main hydrocarbon target of the Syria Euphrates graben area. The experimental results; X-Ray Diffraction (XRD), Scanning Electron Microprobe (SEM) and Electron Diffraction System (EDS) analysis show that the clay minerals of this reservoir are dominated by kaolinite, illite, chlorites and illite-smectite mixture. Kaolinite is the main clay minerals phase found. Morphologically, it’s recorded as hexagonal to pseudo hexagonal platelets or booklet; consist of particles clusters (10 to 15јm micrometre) of crystals arranged as sub to euhedral blocky structures often measure between 20 to 60 јm in length that partially or completely filled pore spaces. Chlorites are commonly occurred as grain coating, or pore-filling / lining phase, its occupy almost 17 % of the clay volume, and composed of well crystallised, euhedral individual plates 2 to 10 µm with a honeycomb morphology, randomly oriented in aggregates that have retained the outlines of the former framework grain. Illite constitutes about 37 %, and identified as grain coating or pore filling phase composed of well-crystallized lath-like blades (10 јm), and short fiber-like morphology partially filled the intergranular pore and has nucleated at the margins of detrital clay surfaces. Illite - smectite mixture is less abundant, constitutes about 20 %, and exists as grain-coating or pore-filling phase, consists of well-developed crystals characterized by platy or wispy edges ranging fr om 2 to 10 µm thick. The early diagenesis of upper Triassic sandstone was characterized first by the mechanically infiltration of the detrital clay, early formation of chlorite, kaolinite and grain-coating illite-smectite. During the burial diagenesis kaolinite precipitation are continued and appears to be change in the morphology with increasing burial depth. The chlorite and illite forming is also minor phase during the burial diagenesis. Illite-smectite mixtures layers also take a place at burial diagenesis stage, wh ere the leaching of the ferromagnesian minerals is being considered to be the source for the necessary ions.
References
1. Shmyrina V.A., Morozov V.P., Bakhtin A.I., Sedimentological and lithogenetic factors determining the reservoir properties of terrigenous rocks (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2014, no. 10, pp. 18-20.
2. Ramm M., Formation of grain - coating chlorite in sandstones; laboratory synthesized vs. natural occurrences, Clay Mineral, 2000, no. 35, pp. 261-269.
3. Burley S.D., Kantorwicz J.D., Waugh B., Clastic diagenesis, In: Sedimentology: Recent developments and applied aspects: edited by Brenchley P.J., Williams B.P.J., Geological Society Special Publication,1985, no. 18, pp. 198-226.
4. Worden R.H., Morad S., Clay minerals in sandstones: A review of the detrital and diagenetic sources and evolution during burial, In: Clay cement in sandstones: edited by Worden R.H., Morad S., International Association of Sedimentologists, Special Publication, 2003, no. 34, pp. 3-41.
5. Ketzer J.M., Morad S., Amorosi, A., Predictive diagenetic clay-mineral distribution in siliciclastic rocks within a sequence stratigraphic framework, In: Clay Mineral Cements in Sandstones, International Association of Sedimentologists, Blackwell Publishing, Oxford, 2003, no. 34, pp. 43-61.
6. Burley S.D., Burial diagenesis, In: The Encyclopedia of the Solid Earth Sciences: edited by Keary P., Blackwell Scientific Publications Oxford, 1993, pp. 72-76.
7. Schmidt V., MacDonald DA., The role of secondary porosity in the course of sandstone diagenesis. In: Aspects of diagenesis: edited by Scholle P.A., Schuldger P.R., Soc Econ, Paleont Miner, Spec. Publ, 1979, no.15, pp. 175-207.
8. Ehrenberg S.N., Aagaard P., Wilson M.J., Fraser A.R., Duthie D.M.L., Depth-dependent transformation of kaolinite to dickite in sandstones of the Norwegian Continental shelf, Clay Miner, 1993, no, 28, pp. 325-352.
9. McKinley J.M., Worden R.H., Ruffell A.H., Smectite in sandstones: a review of the controls on occurrence and behaviour during diagenesis, In: Clay Mineral Cements in Sandstones: edited by Worden R.H., Morad S., International Association of Sedimentologists, Special Publication no. 34, Blackwell Publishing, Oxford, 2003, pp. 109-128.
