Abstract: A particulate matter plug is placed along all or portions of a well to be permanently or temporarily abandoned, the plug being arranged to hinder/reduce fluid flow to surface. The plug consists of a mass of particulate matter composed of naturally occurring and/or synthetically produced granular matter, including gravel, sand, silt, clay and a mixture of these, and preferably of a poorly sorted mass of particulate matter. The granular particulate matter having average particle diameters included in the statistical range of variation of the mass is comprised of particles with an average particle diameter >1/256 millimeters, thus comprising approximately {fraction (2/3 )} of all particles in the mass.