Experimental and theoretical study on influencing factor of fracture width in coalbed methane reservoir

Abstract

Fracture width in coalbed methane (CBM) reservoir is an important parameter for hydraulic fracture and of great significance for studying the permeability of CBM reservoir after being fractured. To study the impact of fracturing position on fracture width, specimens made of similar materials were applied to replace coal rock, hydraulic fracturing experiment was conducted by means of hydraulic fracturing experimental device, and fracture width was measured by displacement meter timely. The effect of other factors on fracture width was analyzed by theoretical analysis. The research results show that fracture width is affected by the position of displacement meter, fracture morphology, natural fracture width, and permeability of coal seam. The fracture morphology of three fractured specimens was different from each other in hydraulic fracturing tests. Fracture morphology of specimen No. 1 is the most complex, and the fracture morphology of specimen No. 1 and No. 2 is all more complex than the one of specimen No. 3. Fracture width fluctuates and increases with the continuous injection of fracturing fluid. The growth rate of fracture width varies with the different position of displacement meter, which is a positive correlation with fracture morphology. Fracture width is inversely proportional to the permeability of coal seam; the permeability of coal seam increases with the decrease of fracture width. Fracture width is proportional to the negative value of natural fracture width, fracture width decreases with the increase of natural fracture width. The research results would provide technical support and theoretical reference for studying fracture width and hydraulic fracturing theory.