balance and dynamic overbalance devices such as pure u2122 guns and pure u2122 chambers available from schlumberger u2122 controlling transient pressure conditions in a wellbore is discussed in u s pat no 7 284 612 which is incorporated herein by reference in its entirety the present application includes embodiments that create a transient pressure plug in the borehole above and below an implosion dynamic under balance event or a dynamic overbalance event for example the transient plug could disrupt the movement and pressure effects of borehole fluids towards the area of dynamic under balance implosion or dynamic overbalance depending on the desired effect also the transient plug could contain the effects of the implosion dynamic under balance or dynamic overbalance effect to a defined region in the wellbore now looking at the figures the device shown in fig1 and 2 has two vented combustion chambers positioned above and below a low pressure chamber or strings of low pressure chambers the low pressure chamber s can be ruptured by the detonation of explosive primer cord rapidly exposing the adjacent borehole to a low pressure shock the primer cord can activate shaped charges to rupture the low pressure chamber and perforating the casing and formation alternatively the.