How seismic has helped to change coal mining in China

Abstract

Coal is the main source of energy in China and accounts for over 65% of the country’s total energy consumption. China’s coal production is the largest in the world and its reserves rank third. Geological reports used for coal mine design and mining production in the past (before 1991, many mines operated without a seismic survey) could only determine faults with displacement larger than 30 m. Such reports fell far below the modern standard needed for mine design and extraction. Because of the poor precision of these geological reports, some mining layouts were unsuitable. Some tunnels and mines have flooded when unexpected geological structures have been encountered. Aware of the enormous economic loss caused by geological unknowns and the potential of high resolution seismic technology, the National Energy Investment Corporation issued a policy document (No.612) in 1991. It required that a seismic survey must be carried out in a coal mine area before any production plan is drawn up. Mining without a pre-production seismic report was forbidden. As a result, the new regulation promoted the application of high-resolution seismic surveys for coal mine construction and production, and marks a landmark in the history of seismic technology in China’s coal industry. From 1991 to 1993, all the seismic surveys were 2D, but it was soon found that the geological reports using 2D were not good enough to meet the needs of coal mine design and production. The first 3D survey in a coal mining area was carried out at Xieqiao coalmine for the Huai Nan Bureau of Mining in 1993. Since then, 3D surveys have been rapidly adopted for coal mines in China. Up to now, 3D surveys account for 95% of all coal mine seismic with 2D surveys making up only 5%. By the end of October 2003, 350 3D surveys projects had been completed covering an area of 600 km2. It has shown that the correct rate of faults with displacement larger than 5 m and caved pillars with a diameter bigger than 20 m verified by seismic survey is over 85% [1]. The detailed geological results have played an important role in optimizing the lay-out of mines. They can also prolong a mine’s production life, improve the safety of the operation, and deliver outstanding economic benefits to coal mining companies in China.