Theoretical considerations on the penetration of powdered metal jets

This paper explores some of the theoretical issues encountered when interpreting the penetration behavior of an oilwell perforating charge, whose jet forms from an unsintered powdered metal (PM) liner. Appropriate treatments of the jetʹs porous compressible nature fill the gap between classical “continuous” and “fully particulated” jet penetration models. Within certain constraints, increasing a penetratorʹs length (even if by distension) increases its hydrodynamic penetration depth, while reducing its impact pressure; and a porous penetrator penetrates deeper than a non-porous penetrator of the same density, length, and velocity. Dynamic target pressure considerations lead to the conclusion that highly distended, low-velocity, PM jets should penetrate moderate-strength geologic targets effectively. After demonstrating that initial transient shock pressures may be much higher than steady-state penetration pressures, we suggest that initial penetration rates may be higher than the steady-state rates. This, in conjunction with the well-known “residual penetration” phenomenon, indicates that a non-continuous jetʹs penetration may be strongly influenced by transient effects.