Abstract: To address the issue of low recovery rates due to long-term polymer plugging in sandstone reservoirs,this study proposes a method of deep-penetration composite chemical deplugging for sandstone reservoirs.By leveraging sand-free deep-penetration fracturing,the deplugging fluid was delivered deep into the reservoir to enhance the deplugging effectiveness. The numerical reservoir simulation is employed to investigate the seepage patterns of the deplugging fluid along deep-penetration fractures,and a production prediction model for deep-penetration deplugging is constructed to evaluate the impact of factors such as the length of deep-penetration fractures and the amount of deplugging fluid on the deplugging effect. The study shows that:after the injection of the deplugging agent into the formation,the agent forms a dumbbell-shaped distribution in the affected area,improving the permeability of the reservoir.As the length of the fracture increases,the effective deplugging area gradually enlarges.With the increase in construction flow rate,the effective deplugging area first increases and then decreases.Both the fracture half-length and the amount of deplugging fluid have a certain impact on the deplugging effect,with the optimal deplugging effect achieved when the deep penetration fracture half-length is approximately 1.4 times the radius of the contamination zone.The findings of this study can provide a reference for the design of deplugging and production increase processes in sandstone reservoirs.

Key words: sandstone reservoir, deep-penetration fracturing, chemical deplugging, production capacity, numerical simulation