one embodiment while the well is producing after perforations in the formation 512 have been formed the atmospheric chamber in the container 510 is explosively opened to the wellbore this technique can be used with or without a perforating gun when used with a gun the atmospheric container allows the application of a dynamic underbalance even if the wellbore fluid is in overbalance just prior to perforating the atmospheric container 510 may also be used after perforation operations have been performed in this latter arrangement production is established from the formation with the ports 516 of the atmospheric container 510 explosively opened to create a sudden underbalance condition the explosively actuated container 510 in accordance with one embodiment includes air or some other suitable gas or fluid inside the dimensions of the chamber 510 are such that it can be lowered into a completed well either by wireline coiled tubing or other mechanisms the wall thickness of the chamber is designed to withstand the downhole wellbore pressures and temperatures the length of the chamber is determined by the thickness of perforated formation being treated multiple ports 516 may be present along the wall of the chamber 510 explosives are placed inside the atmospheric container in the proximity of the ports in one arrangement the tool string.