The Mesopotamian Sedimentology researches..

Sedimentological and Petrophysical study of reservoir  of Nahr Umr formation,

 in Luhais field, south of Iraq

Haider  M.  jasim

Geology Department, College of Science

University of Basrah, Iraq

(E-Mail: hydersam@yahoo.com)
 

Abstract

    Nahr-Umr Formation (Albian) was studied in Luhais Oil field at southern Iraq. The study focused on the sedimentological and reservoir aspect including facies analysis, mineralogy, petrology and petrophysics. The formation composed of mostly sandstones, siltstones and claystones. Quartz is the main mineral constituent in the sandstones, whereas, kaolinite is the predominant clay mineral in the mudstones with minor amounts of mixed layer Illite- smectite. The sandstones were subjected to anumber of diagenetic processes such as compaction and cementation (silica and carbonate cement). Petrographic studies showed that the sandstones are dominated by opaques and ultrastable minerals (Tourmaline and Rutile). The lithological succession in the studied area was divided into six sedimentary lithofacies : claystone lithofaces (A), clayey siltstone lithfacies (B), lenticular bedded sandstone mudstone lithfacies (C) , parallel bedded sandstone siltstone lithofacies (D), planer cross bedded sandstone lithofacies (E), and parallel bedded sandstone lithofacies (F). Depositional environment of Nahr-Umr Formation could be beach affected by delta processes, and deposited during Albian transgression. Secondary environments were also recognized such as; Shelf, transition zone, lower shoreface, middle shoreface, and upper shore face. The rocks of Nahr- Umr formation in the studied area have been divided into four types of reservoir rocks; Good reservoir rock, medium reservoir rock, poor reservoir rock, and poor-Non reservoir rock. Good reservoir and poor reservoir rocks are attributed to the parallel laminated sandstone and parallel laminated sandstone – siltstone lithofacies respectively. The sub environments of middle shoreface and upper shoreface are characterized by good reservoirs.

Unpublished M.Sc. Thesis, University of Basrah, College of Science, 2001