Abstract: According to a preferred embodiment, a dynamic underbalance device has a longitudinally extending tool string including an underbalance part. A first overbalance part is above the underbalance part and a second overbalance part below the underbalance part. Upon application of underbalance from the underbalance part and overbalance from the overbalance part, the overbalance and underbalance interact to isolate the underbalance.

Abstract: A downhole tool assembly for use in a wellbore includes a tubular body carrying an explosive which is selectively detonated to create a dynamic underbalance or overbalance effect in the wellbore. The tubular body has opposite ends provided with plug assemblies including plug elements movable between a normally collapsed state and an actuable expanded state. The plug elements are adapted to be actuated to the expanded state between the tubular body and an outer extent of the wellbore before the creation of the dynamic underbalance or overbalance effect to isolate a discrete segment of the wellbore to which the dynamic underbalance or overbalance effect is confined.

Abstract: A method for use in a wellbore includes the steps of providing an elongated, closed tubular body defining an internal chamber wherein the tubular body has an external surface formed with treated areas and an elongated recess extending longitudinally of the tubular body and running through the treated areas; retaining a detonating device in the recess adjacent the external surface of the tubular body; positioning the tubular body with the detonating device in a wellbore adjacent perforation tunnels previously formed in a surrounding well formation and filled with debris; and activating the detonating device to rupture the tubular body inwardly along the external surface forming the recess at the treated areas to expose the chamber within the tubular body to a dynamic underbalanced pressure condition such that fluid from the wellbore and debris from the perforation tunnels is drawn through the wellbore and into the chamber.

Abstract: A downhole tool assembly for use in a wellbore includes a tubular body carrying an explosive which is selectively detonated to create a dynamic underbalance or overbalance effect in the wellbore. The tubular body has opposite ends provided with plug assemblies including plug elements movable between a normally collapsed state and an actuable expanded state. The plug elements are adapted to be actuated to the expanded state between the tubular body and an outer extent of the wellbore before the creation of the dynamic underbalance or overbalance effect to isolate a discrete segment of the wellbore to which the dynamic underbalance or overbalance effect is confined.

Abstract: According to a preferred embodiment, a dynamic underbalance device has a longitudinally extending tool string including an underbalance part. A first overbalance part is above the underbalance part and a second overbalance part below the underbalance part. Upon application of underbalance from the underbalance part and overbalance from the overbalance part, the overbalance and underbalance interact to isolate the underbalance.

Abstract: A method for use in a wellbore includes the steps of providing an elongated, closed tubular body defining an internal chamber wherein the tubular body has an external surface formed with treated areas and an elongated recess extending longitudinally of the tubular body and running through the treated areas; retaining a detonating device in the recess adjacent the external surface of the tubular body; positioning the tubular body with the explosive in a wellbore adjacent perforation tunnels previously formed in a surrounding well formation and filled with debris; and activating the detonating device to rupture the tubular body inwardly along the external surface forming the recess at the treated areas to expose the chamber within the tubular body to a dynamic underbalanced pressure condition such that fluid from the wellbore and debris from the perforation tunnels is drawn through the wellbore and into the chamber.