Mining Evaluation of Sulfur Deposits in Al-Mishraq Area Using Geostatistical Method

Abstract

The area of the study is located in northern Iraq on the western side opposite the confluence of the Tigris River with the upper Zab tributary, about 45 km southeast of the city of Mosul within the Hamrin-Makhoul zone belonging to the foothills zone within the unstable area. The area contains rocks of many formations ranging in age from the Lower Miocene to the Quaternary, and includes the formations of the Euphrates, Fatha, and Quaternary deposits. Sulfur deposits are present in the Fatha formation within the productive bed which contains three major sulfur-bearing horizons or zones separated by several heterogeneous layers of marly claystone and dolomite limestone of different thicknesses. The formation of sulfur due to the processes of reducing gypsum or anhydrite with the availability of hydrocarbons and the action of anaerobic bacteria, where hydrogen sulfide gas H2S is produced, which is later oxidized by groundwater, forming sulfur ore with the help of other factors represented by tectonic and hydrogeological factors.

The mineral reserves of sulfur deposits were recalculated and estimated using the geostatistical method, as it is one of the modern applications adopted in the Rockwork-14 program, which takes into account the location of each model in relation to the other within the mineral deposits extensions and even outside the boundaries of those extensions, which gives high accuracy and reliability about the amount of reserves depending on the group Among the important criteria, such as thickness, concentration of the ore, and density, the reserve of sulfur in the Mishraq sulfur field-1 was estimated at 121,230,554,68 tons.

The validity and suitability of using the open mine method for extracting sulfur in the study area was discussed based on a decisive and important  factor, which is the stripping ratio, which determines the type of appropriate extractive method, and it was equal to 6 for the entire study area, a large value that exceeded the maximum  permissible limit of  5. This method is not economically feasible due to the high extractive cost and the presence of sulfur at different depths ranging between 80-230 m as well as the presence of environmental and geological problems that hinder the use of this method in sulfur extraction.

The study was based on the data obtained for a group of (9) exploratory wells that were drilled in the region.