The role of structural factors in directing methane and carbon dioxide to the Nosud water transmission tunnel (Azgeleh - northwest of Kermanshah)

Nosud water transfer tunnel with a length of 45 km has been constructed to guide and transfer water in the northwest of Kermanshah. The tunnel passes through several anticlines and synclines and as soon as its axis enters the Garo and Gurpi formations, gases with a volume of more than 400 ppm are drained into the tunnel, which is mainly related to the Azgleh and Kurdish Qasman anticlines. In the Zagros Basin, the Garou and Gurpi Formations are known as high potential oil source rocks. In the study area, despite the predominant type III kerogen, which is mainly of dry origin, a large volume of gases, mainly methane and carbon dioxide, are found. Due to the expansion of Garo and Gurpi formations in the region, gas-prone zones in the tunnel axis are divided into four parts A, B, C, D, which is the largest volume of gas produced in the Kurdish anticline of Qasman and is related to zone D. The gases produced from these areas along with a large volume of water are led into the tunnel through tectonic fractures, which are mainly joints and faults, among which faults play a very important role in the Kurdish anticline of Qasman and the anticline of the herd.