Method and plugging material for reducing formation fluid migration in wells

摘要

The invention relates to a method to hinder/reduce the migration of formation fluids in wells, primarily in connection with plugging of oil wells. A mass of particulate matter consisting of naturally occurring and/or synthetically produced granular material, which may be suspended in a suitable liquid, is placed in or around the well casings (10, 12, 14 and 16) and production tubing (28) to form a plug. The particulate material mentioned can replace conventional mechanical plugs (40, 44, 48) and cement plugs (42, 46, 50). The particulate material plug (52) must have a sufficient length in the well, the particulate material must be suitably sorted and packed and have suitable chemical/physical properties, such that the permeability of the plug (52) becomes sufficiently small that the well is effectively plugged since the time required for formation fluids, e.g. oil, to migrate through the plug may be several thousand years. The plug of particulate matter (52) can also change in shape and adapt to possible geometry changes in the well, for example as a consequence of displacements in the Earth's crust or corrosion of metals in the well, and thereby hinder/minimise possible leaks.