Abstract
Perforations are used to flow hydrocarbons into a well. Impeding that flow are damaged zones from drilling and the crushed zone lining the walls of perforation tunnels into the rock. In addition, charges can affect a region beyond the crushed zone. This region is termed the "fracture damage zone," and the nature of this region is examined in this paper. The fracture damage zone is the area where the concrete model shows altered effects. This region of damage is not necessarily failed, but is the most likely region of fracture. This work discusses the use of a shock hydrocode to delineate this region. Because the hydrocode is a continuous code, specific fracture paths are not predicted. The code is run for big hole (BH). deep penetration (DP), and fracture (Frac) shaped charges. The damaged region is compared for the types of shaped charges. Simulation results indicate that the region of fracture damage follows the bow shock. This semicircular bow shock region continues propagation after the jet has stopped, but eventually diminishes outward from the jet origin. Generally, the BH charge has a wider damage region than the DP charge, with the DP charge damage region being narrower and deeper than the BH (because of the depth of penetration). The damage zone of the Frac charge is between those of the BH and DP charges. In addition, the damaged region may not be sufficiently affected to actually create failure caused by fractures. "Distance" to the fracture limit is characterized. This ready-to-fracture region is discussed in terms of making it a failed fracture region by external influences, such as propellant stimulation.
