The Physics of Fine-Particle Movement Through Permeable Aquifers

The movement of fine particles through porous, permeable materials is closely interwoven with the migration of soluble ions. Since either the particles orthe ions can represent an economic mineral accumulation as a consequence ofgeochemical concentration, it is of great importance to mineral explorationefforts to be able to establish the parameters that influence particulatemigration through aquifers. Not only are economically interesting depositsformed by such migration, but they also may be ruined, as in the case of manyoil fields where standard secondary recovery methods have caused plugging ofthe productive formations. Recent experimental work has shown close alliance between the relative movement of both trace ions and particles and the over-all concentration of common salts dissolved in ground water. Most importantly, the spacial stability of fineparticles such as the sesquioxides and the clays in formations is dependent onthe nature of the anionic portion of the dominant salt in solution. These results have great potential, applied in exploration or exploitation programs for minerals. Not only do they provide answers for particulate migration problems in the oil fields and ore concentration mechanisms in the uranium deposits, but also they explain the untoward migration of certain radioisotopes from waste storage ponds or cribs at the national reactor-fuel reprocessing plants. By careful development and engineering practice, fine particles tagged with almost any radioactive or activatable ions may become one of the most useful tools in tracing subsurface movement of fluids. Introduction Considerable concern has been expressed by several industries during the past several decades about the effects of fine-particulate matter suspended in water passing through permeable rock. An early concern of the petroleum industry included the problem of subsurface reservoir plugging by fine particles during secondary production operations. More recently, the atomic energy industry has been concerned with particulate migration because of the movement of radioactive ions. Even the interest in applications of nuclear explosions underground has included concern over the effects of the fine-particulate matter that makes up large portions of the rubble produced by the explosion.