Theory of gas traps in stope and its application in ground extraction of abandoned mine gas: Part 2 – The development suitability evaluation of gas trap and its application.

As well-known, not all abandoned mines have abundant AGM resources. Also not all abandoned mines with abundant AGM resources are suitable for surface gas development. It is a very timely and valuable work on how to scientifically and quickly optimize the target abandoned mines suitable for surface development from many abandoned mines. This research includes three parts, e.g., the development suitability evaluation of the trap in the stope, the optimization of target abandoned mine and the field application. In the first part, the evaluation system and method of trap development suitability are established. AGM resources, storage conditions, the accumulated water and the developing economy are selected as the development suitability evaluation indexes. Each evaluation index is divided into three levels, and the method to determine the grading standard value of each evaluation index is proposed. The multi-factor comprehensive evaluation method of grey relational analysis is used in the evaluation and divided the trap into three types: suitable trap, less suitable trap and unsuitable trap according to the degree of development suitability. In the second part, the optimization method of the target abandoned mine is proposed based on the theory and development suitability of the gas trap. Firstly, screen out abandoned mines with obvious safety risks or poor economic benefit prospect of gas development. Secondly, determine the number of gas traps and suitable traps in each candidate. Thirdly, the candidate abandoned mine with the largest total gas resources in suitable traps is selected as the most favorable abandoned mine. In the third part, taking a medium-sized coal mine in the southeast of Shanxi Province as a field test mine, the gas trap determination, resource calculation and development evaluation of 17 gobs were carried out. The evaluation results show that none of them are suitable trap. The results of surface gas development in the gobs of the mine confirmed the evaluation results. • Not all closed gobs can be form traps, and become recoverable gas reservoirs. • Established the evaluation system for development suitability of gas traps. • The optimization method of target abandoned mine is established. • The theory of gas trap and its evaluation have been applied in the field. [ABSTRACT FROM AUTHOR]