Apparatus and method for increasing the amount of dynamic underbalance in a wellbore

A downhole tool for use in a wellbore comprising:

• an elongated tubular body closed and sealed at opposite ends thereof and defining an internal chamber, the tubular body having an external surface formed with a recess extending inwardly and longitudinally of the tubular body;
• and
• a detonating device positioned adjacent the external surface of the tubular body and located within the recess,
• wherein the tubular body is constructed of a metal material having brittle areas formed along the external surface containing the recess.

A downhole tool for use in a wellbore comprising:

• an elongated tubular body closed and sealed at opposite ends thereof and defining an internal chamber, the tubular body having an external surface formed with a recess extending inwardly and longitudinally of the tubular body;
• and
• a detonating device position adjacent the external surface of the tubular body and located within the recess,
• wherein the tubular body is designed to rupture inwardly into openings at selected areas of weakness provided along the external surface forming the recess upon firing of the detonating device.

A downhole tool for use in a wellbore comprising:

• an elongated tubular body closed and sealed at opposite ends thereof and defining an internal chamber, the tubular body having an external surface formed with a recess extending inwardly and longitudinally of the tubular body;
• and
• a detonating device positioned adjacent the external surface of the tubular body and located within the recess,
• wherein the detonating device is directly engaged in the recess with certain sections of the tubular body designed to fail and other sections of the tubular body designed not to fail upon firing of the detonating device.

A method for use in a wellbore, the method comprising the steps of:

• providing an elongated closed tubular body defining an internal chamber, the tubular body having 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 underbalance pressure condition such that fluid from the wellbore and debris from the perforation tunnels are drawn through the wellbore and into the chamber.

A method of making a downhole tool for use in a well, the method comprising the steps of:

• supplying an elongated blank metal sheet having spaced apart side edges, an upper surface, a lower surface and a generally constant thickness;
• forming stress raisers in areas of the upper surface of the metal sheet along a length thereof;
• forming an elongated recess in the upper surface of the metal sheet running through the areas of the stress raisers;
• rolling the metal sheet and welding the side edges together to form a tubular body with the upper surface defining an external surface;
• treating the tubular body to form a brittle structure in the areas of the stress raisers;
• providing end cap structure on the tubular body;
• and
• retaining a detonating device in the elongated recess formed in the external surface of the tubular body.

A method for use in a wellbore, the method comprising the steps of:

• providing an elongated closed tubular body defining an internal chamber, the tubular body having an external surface formed with an elongated recess extending longitudinally of the tubular body;
• 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 containing fluid 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 to expose the chamber within the tubular body to a dynamic underbalance pressure condition such that fluid from the wellbore and debris from the perforation tunnels are drawn through the wellbore and filled into the chamber to clean the perforation tunnels.