U.S. Patent No. 7,243,725 - Surge Chamber Assembly And Method For Perforating In Dynamic Underbalanced Conditions (Jul. 17, 2007)

A surge chamber assembly (70) for use in a wellbore includes a housing (80) having one or more openings (112), a surge chamber (100) and a combustion chamber (98). The openings (112) provide fluid communication between the exterior (82) of the housing (80) and the surge chamber (100). A sleeve (114) is slidably positioned within the housing (80) and has a first position wherein fluid communication through the openings (112) is prevented and a second position wherein fluid communication through the openings (112) is allowed. A combustible element (124) is positioned in the combustion chamber (98) such that combusting the combustible element (124) generates pressure in the combustion chamber (98) that actuates the sleeve (114) from the first position to the second position.