1. n. [Well Completions]

The movement of fine clay, quartz particles or similar materials within the reservoir formation due to drag forces during production. Fines migration may result from an unconsolidated or inherently unstable formation, or from use of an incompatible treatment fluid that liberates fine particles. Unlike sand migration that is best stabilized, the material mobilized in fines migration should be produced to avoid near-wellbore damage. Fines migration causes particles suspended in the produced fluid to bridge the pore throats near the wellbore, reducing well productivity. Fines can include different materials such as clays (phyllosilicates smaller than 4 microns) and silts (silicates or aluminosilicates with sizes ranging from 4 to 64 microns). Kaolinite and illite are the most common migrating clays. Damage created by fines usually is located within a radius of 3 to 5 ft [1 to 2 m] of the wellbore, but can also occur in gravel-pack completions. In sandstone formations, hydrofluoric acid [HF] mixtures are used to dissolve fines. In carbonate formations, the goal is not to dissolve but rather to disperse fines in the wormholes, so hydrochloric [HCl] acid is used as the treatment fluid.

See related terms: gravel pack,  induced particle plugging,  pore throat,  treatment fluid,  wormhole