Technical thinking on ectopic injection and storage of mine area water resourcesunder the coordinated exploitation of coal and water background in Ordos Basin

During the process of Jurassic coal mining activities in the Ordos Basin, the mine water inflow is constantly increasing. In order to alleviate the problems such as the increasing expenditure of mine water advanced treatment and the difficulty of largescale treatment, an experimental investigation on mine water deep injection was put forward based on the scientific concepts of coalwater coordinated mining and waterpreserved coal mining in the study area. Firstly, the contradictions between coal mining and water resources protection in the Ordos Basin were expounded, including the relationship among mine water disaster prevention, regional water resources preservation and ecological environment protection in mine areas. Secondly, the bottleneck problems of mine water treatment under the coordinated development of coal and water were clarified combined with the investigation and statistics of the water quality characteristics of 38 coal mines in the study area. The conventional ions in mine water exceeding the standard Ⅲ value of Standard for Groundwater Quality (GB/T 14848—2017) account for 68.4%, meanwhile iron and manganese account for 20%, and the characteristics of high salt and high fluorine were obvious in the study area. At present, the mine water treatment cannot meet the demand of relatively low cost and large scale at the same time. Then, the authors put forward "three decrement and one treatment" technical approaches of water resources protection and ectopic injection in the mine areas, including mining related aquifers ectopic injection, minedout space water ectopic injection, open pit water ectopic injection and mine water with special components ectopic injection, and the feasibility of the experimental research is qualitatively compared. The authors expounded in detail the theory and technology framework, technical contents and technical bottlenecks about ultradeep injection and storage, and conducted a demonstration project for high TDS (total dissolved solid) mine water treatment in the study area, based on the engineering insitu case of ultradeep injection and storage at a mine in the Ordos Basin. Finally, the authors proposed that weak acid and weak alkali (44%) and high TDS mine water (69%) should be stored by ultradeep injection derived from the statistical analysis of the TDS values of 87 coal mines and the pH values of 133 coal mines in China, so as to reduce the consumption and waste. At the same time, the cost of mine water advanced treatment is reduced. This paper pointed out that mine water deep injection has significant application value in Northern China, and even some other coal mining areas of China.