Study on Distribution Law of Coal Seam Gas and Hydrogen Sulfide in Area Affected by Abandoned Oil Wells

In order to fully grasp the characteristics and distribution of coal seam gas and hydrogen sulfide in the affected area of abandoned oil well, through theoretical analysis and field investigation, the occurrence state, original distribution and mining-induced emission rule of gas and hydrogen sulfide in coal seam in the affected area of abandoned oil well were obtained. The results show that, under the action of gas pressure (concentration), when the casing is broken or the well itself is open hole, a large amount of hydrogen sulfide, methane and other gases in the oil reservoir will gradually escape to the coal-bearing strata and adsorb in coal seam. Hydrogen sulfide in coal mainly exists in the adsorption state, and only under the influence of mining will be released in large quantities. The concentration distribution of hydrogen sulfide in boreholes in the affected area of abandoned oil well was consistent with that of hydrogen sulfide gushing from mining and the closer to the center of the abandoned well, the higher it was, and the lower it was as it moved away from the well. The distribution of gas content in coal seam along the center distance of oil well shows a trend of power function decreasing and the concentration distribution of gas emission during mining is consistent with that of hydrogen sulfide emission.