Mineralogical and Geochemical Study of the Asmari Group in the Fauqi Oil Field in Maysan, Southeastern Iraq

Abstract

The presence of clay minerals of any kind and in any quantity and distribution pattern in hydrocarbon wells causes many problems in the qualitative assessment of the reservoir, A geochemical and mineralogical study are conducted on the reservoir units of the Asmari Group (early Miocene-Oligocene) to identify the clay mineral types present in the reservoir and the effect these clay minerals have on the reservoir's petrophysical properties. the Jeribe Formation (unit A) and the Upper Kirkuk Formation (unit B) are represented the main units of the Asmari reservoir ten samples from the Asmari group of the Fauqi oil field were chosen: five from the southern dome denoted by a number 65 and the same from the northern dome denoted by a number 64, Samples 1 and 2 represent unit A, while samples 3, 4, and 5 represent unit B. The mineralogical study showed that the non-clay minerals are represented by dolomite, calcite, anhydrite, quartz, and halite, while the clay minerals are represented by Illite, kaolinite, and chlorite, the geochemical analysis showed that the main oxides in the reservoir units of the Al-Asmari group are: silica, alumina, iron oxide, calcium oxide, magnesium oxide, sodium oxide, potassium oxide, titanium dioxide, sulfate, and chlorine, the highest percentage of the main oxides are calcium oxide, sulfate, and silica, respectively, and that the northern dome has a higher percentage of calcium, magnesium, sulfate, and the loss of ignition than the southern dome, while the percentage of silica and alumina in the southern dome is higher than its percentage in the northern dome which indicates a high percentage of clay minerals in the southern dome. The positive correlation between potassium and sodium and the negative correlation between potassium and calcium indicates that the Illite is of the Na-Illite type. Due to its lower charge Na and weak hydrogen bonds, Na-illite has greater dispersibility than Ca-illite and is present in all samples, making it the most clay mineral affecting the petrophysical properties in the study area.