Damage mechanism of coal powder on fracture conductivity

Abstract：In order to investigate the migration law, damage mechanism and damage degree of coal powder in the prop- pant pack,the authors used FCES-100 fracture long-term flow conductometer to simulate the process. Experiment re- sults show that coal powder is likely to intrude into proppant pack and difficult to discharge with water, causing serious damage on conductivity and the damage raises dramatically with the increase of concentration of coal powder. Accord- ing to analysis, the main causes for the damage are the adhesion & accumulation of coal powder, and the bridge plug in pore throat by it. Coal fines with smaller diameters are more vulnerable to move and gather together in the pack, and have a bigger potential to damage the conductivity. It is an effective way to improve conductivity by employing proppant in smaller diameters to entrap coal powder. And also, backflow immediately after the treatment is helpful to discharge the coal powder and reduce its retention in the fracture. Then, to avoid the powder conglomeration and plug the flow path, it is necessary to maintain a steady gas production.