Mini-severing and back-off tool with pressure balanced explosives

A method of releasing a threaded pipe joint within a pipe string comprising the steps of:

• providing a tube having a bore space enclosed by a tube wall;
• providing an initiation housing;
• placing a booster explosive within said initiation housing;
• securing a first end of said tube to said initiation housing;
• penetrating said tube wall with at least one aperture to equalize pressure internal and external to the tube wall;
• inserting a plurality of explosive pellets into the bore space;
• biasing against one end of the plurality of explosive pellets to urge an opposite end of the plurality of explosive pellets into detonation proximity with the booster explosive;
• positioning the tube within a pipe string flow bore adjacent to a threaded pipe joint;
• applying a torque on the pipe string for disassembling the pipe string;
• and
• detonating at least one of the plurality of explosive pellets.

A method of releasing an intended pipe joint threaded within a pipe string, wherein said method comprises the steps of:

• tabulating values representing a weight of explosive distributed over a unit length corresponding to a type of pipe, a size of pipe, a well depth location of the intended pipe joint, a density of fluid within a well, or combinations thereof, such that when the explosive is detonated adjacent to the intended pipe joint and under moderate torque, the detonation will initiate the release of the intended pipe joint;
• contiguously aligning a plurality of explosive pellets having a concentration of explosive corresponding to the tabulated value adjacent to the intended pipe joint within a tubular bore;
• venting a wall of the tubular bore with at least one aperture to equalize pressure within the tubular bore to pressure external to the tubular bore;
• positioning the tubular bore within the pipe string proximate to the intended pipe joint;
• applying a moderate torque to the pipe string;
• and
• detonating the plurality of explosive pellets simultaneously with the application of the moderate torque to disassemble the pipe string.

A downhole mini-severing and back-off tool apparatus comprising:

• a firing head secured to an initiation housing, wherein the firing head comprises a detonator therein;
• a pellet tube secured in the initiation housing, wherein the pellet tube comprises an enclosure wall;
• a plurality of explosive pellets in contiguous alignment within the enclosure wall of the pellet tube;
• at least one of said plurality of explosive pellets positioned within ignition proximity of said detonator;
• a bias at a first end of the plurality of explosive pellets, wherein the bias urges a second end of the plurality of explosive pellets in detonation proximity with the booster explosive;
• and
• at least one aperture in the enclosure wall of the pellet tube, wherein the at least one aperture substantially equalizes a pressure within the enclosure wall of the pellet tube with a pressure external of the enclosure wall of the pellet tube prior to detonation.

A method of releasing a threaded pipe joint within a pipe string comprising the steps of:

• providing a tube having a bore space enclosed by a tube wall;
• providing an initiation housing;
• securing a first end of said tube to said initiation housing;
• providing a firing head having an explosive detonator therein;
• securing said initiation housing to said firing head;
• penetrating said tube wall with at least one aperture to equalize pressure internal and external to the tube wall;
• inserting a plurality of explosive pellets into the bore space;
• biasing against one end of the plurality of explosive pellets to urge an opposite end of the plurality of explosive pellets into detonation proximity with said detonator;
• positioning the be within a pipe string flow bore adjacent to a threaded pipe joint;
• and
• applying a torque on the pipe string and simultaneously detonating at least one of the plurality of explosive pellets for disassembling the pipe string.