Restricting fluid passage and novel materials therefor

摘要

Water problems in the production of oil or gas from subterranean formations is addressed by providing a method of restricting passage of a fluid from a first location to a second location in a subterranean formation by injecting into the formation a formulation comprising a first material, for example a dialdehyde, arranged to cross-link a second polymeric material, for example a polyvinyl alcohol, thereby to form a polymeric material of high viscosity which may block the passage between the first and second locations.