Subsurface Coal Fire Mapping in Patherdih Colliery, a Part of the Jharia Coal Field, India

Abstract

Coal fires are a universal problem in worldwide coal mining areas. They burn out precious coal resources, hinder mining activities and pose a danger to man and machine, besides leading to environmental pollution and land subsidence problems. In this context, high resolution magnetic survey offers a powerful tool for the detection, delineation and monitoring of coalfires. The Jharia coalfield in India is known for its high grade coal and associated coal fires. The valuable coal reserves are destroyed in the subsurface due to fire, before their exploitation. The present study deals with the mapping and understanding of subsurface coal fire on the basis of magnetic properties of materials and their changes with temperatures above or below the Curie temperature. The coal burning heat rising above Curie temperature results in a loss of natural magnetism in nearby area. Small regions, called domains, within the crystal structure reorient themselves which upon cooling; align themselves more or less in the direction of the ambient magnetic field. This remanent magnetism may be several orders of magnitude greater than the natural magnetism. The minerals which are formed and their respective magnetic strengths depend on the temperatures reached and the amount of oxygen available. Magnetic data acquisition has been carried out using high resolution GSM-19T proton precession magnetometer in gradient mode. The acquired magnetic data have been processed and analyzed using Geosoft Oasis Montaj software to study magnetic field anomaly of Patherdih Colliery in Jharia coal field, India for mapping and understanding of subsurface coal fire. The processed data provide a clear indication of location of active coal fire affected area. This repeated study could help for characterization of dynamics of coal fire of the region.