Permeability enhancement of coal-bearing propped fractures using blockage removal agent treatments in coalbed methane reservoirs

The generation and transport of coal powder has caused great harm to coal reservoir channeling conductivity, affecting the capacity of coalbed methane wells, causing the failure of engineering equipment and great distress to production, while current unblocking methods have many shortcomings. Dispersants, foam stabilizers, and inorganic salt electrolytes were selected in this study as the main components of blockage removal agents, and the wettability and synergistic effects of each component were tested. The results showed that the wettability was best when the ratio of the blockage removal agent was 0.8% SDS + 0.6% BS-12 + 0.8% NaCl, which was 1.57 times higher than that of a single dispersant. The surface tension of blockage removal agent was 64.75% lower than that of clear water. The discharge rate of the pulverized coal particles under the action of the optimum blockage removal agent reached more than 40%, which was more than twice that of clear water. The discharge of the pulverized coal was more than 1.2 times that of the common dispersant formula. The gas-liquid permeability was 4.21 times higher than that obtained with water injections, and 1.45 to 2.91 times higher than that of the commonly used dispersant formulations. This work is helpful to provide a practical guide for the efficient cleaning of sedimentary retained pulverized coal in low-yield coalbed methane wells. This research result is very important to ensure the efficient and stable development of coalbed methane.