1. n. [Enhanced Oil Recovery]

A large, empty channel that can penetrate several feet into the formation, caused by the nonuniform dissolution of limestone or dolomite by hydrochloric acid [HCl]. Wormholes are created during matrix stimulation or acid fracturing of carbonate formations. The purpose of matrix stimulation is to create highly conductive wormholes to bypass damage. However, in fracture acidizing, wormholing is a problem, since it is an unwanted diversion of the live acid from the hydraulic fracture system, which causes a reduction of the etched fracture length.

See: hydraulic fracturing

2. n. [Heavy Oil]

A high-porosity, high-permeability channel that develops when heavy oil is produced simultaneously with sand (during cold heavy oil production with sand, or CHOPS). Wormholes develop in a radial pattern away from the borehole and can extend 150 m [492 ft] from the borehole. The development of wormholes can cause reservoir pressure to fall below the bubblepoint, resulting in dissolved gas coming out of solution and forming foamy oil.