Cyclic inert gas injection - an alternative approach to stimulate gas drainage from tight coal zones

Traditional methods of coal seam gas drainage depend on reducing the reservoir pressure to enable gas desorption from the coal matrix. Studies in coal mine gas drainage, particularly in coal seams that are deeply undersaturated and have low permeability, found the rate of reservoir pressure reduction was prohibitively slow. In such conditions, lengthy production delays were experienced while additional gas drainage drilling was undertaken in an attempt to reduce seam gas content below specified threshold limits. Such additional drilling represents a high additional operating cost and typically yields low total gas production whilst adversely impacting the mine’s gas drainage drilling schedule and potentially leading to coal production delays. kA novel method to enhance gas drainage from tight coal zones, known as cyclic inert gas injection, which does not rely on reservoir pressure reduction to stimulate gas flow is proposed.