Experimental and simulation analysis of jet-perforated rock damage

The finite-element method (FEM) is employed to evaluate stress distribution around a perforation tunnel with a sandstone formation. Experimental data are used to confirm the results of theoretical study. In the model, the eff ect of jet pressure, jet temperature, and the combination of both on format ion are studied separately. The results indicated that a 3.5-g RDX charge i s capable of disturbing rock formation up to 5 in. longitudinally and 2 in. radially. The extent of this damage zone for a 10.5-g RDX charge is 8 in. longitudinally and 4 in. radially. The linear effect is within the first fe w inches of the perforation tunnel entrance. In this region, rock grains ar e under an intensive sudden shock-pressure wave of 2 to 4 million psi for a fraction of a microsecond. As a result, the rock's physical structure will change to metamorphous with a lower bulk density than that of unshocked ro ck, causing a sudden decrease in formation porosity and, hence, formation p ermeability.