Sidewall core gun

Claim 1

An apparatus for taking core samples from the sidewall of a borehole in a well, said apparatus comprising: a string of drill pipe; at least one gun housing connected to the downhole end of said drill string; at least one coring bullet radially disposed within said gun housing, said coring bullet arranged for securing formation samples from the sidewall of said borehole; a charge assembly for propelling said coring bullet toward the sidewall, said charge assembly comprising: a detonatable cord having a diameter substantially in the range of approximately 0.125 to 0.150 inches extending generally axially through said housing from the uphole to the downhole end thereof; at least one cartridge assembly disposed within said housing between said cord and said bullet, said cartridge assembly including a pyrotechnic charge for propelling said bullet, said cartridge assembly comprising: a case having a substantially solid portion and a substantially hollow portion, said case being oriented with the solid portion thereof adjacent to said cord; a passage having a diameter of approximately 0.065 to 0.070 inch through the solid portion of said case connecting the hollow portion thereof to the exterior thereof adjacent to said cord; a pyrotechnic charge disposed within said case, said pyrotechnic charge comprising: a propellant charge disposed within the hollow portion of said case, said propellant charge having a mixture of components being designed to deflagrate on ignition thereof having a low deflagration velocity in the range of approximately 650 to 700 feet per second; and a first transfer charge disposed within said passage, said first transfer charge being arranged to burn on ignition thereof having a burn velocity of approximately 3,000 to 4,500 feet per second and thereby transfer ignition through the passage of said case to the hollow portion of said case; and means for enclosing said charge within said case; and means for igniting said cord; and a cable connecting said coring bullet to said housing, whereby said bullet may be retrieved from the sidewall.

Claim 2

An apparatus for taking core samples from the sidewall of a borehole in a well, said apparatus comprising: a string of drill pipe; at least one gun housing connected to the downhole end of said drill string; at least one coring bullet radially disposed within said gun housing, said coring bullet arranged for securing formation samples from the sidewall of said borehole; a charge assembly for propelling said coring bullet toward the sidewall, said charge assembly comprising: a detonatable cord having a diameter substantially in the range of approximately 0.125 to 0.150 inches extending generally axially through said housing from the uphole to the downhole end thereof; at least one cartridge assembly disposed within said housing between said cord and said bullet, said cartridge assembly including a pyrotechnic charge for propelling said bullet, said cartridge assembly comprising: a case having a substantially solid portion and a substantially hollow portion, said case being oriented with the solid portion thereof adjacent to said cord; a passage having a diameter of approximately 0.065 to 0.070 inch through the solid portion of said case connecting the hollow portion thereof to the exterior thereof adjacent to said cord; a pyrotechnic charge disposed within said case, said pyrotechnic charge comprising: a propellant charge disposed within the hollow portion of said case, said propellant charge having a mixture of components being designed to deflagrate on ignition thereof having a low deflagration velocity in the range of approximately 650 to 700 feet per second; and a first transfer charge disposed within said passage, said first transfer charge being arranged to burn on ignition thereof having a burn velocity of approximately 3,000 to 4,500 feet per second and thereby transfer ignition through the passage of said case to the hollow portion of said case; and means for enclosing said charge within said case; and means for igniting said cord; and a cable connecting said coring bullet to said housing, whereby said bullet may be retrieved from the sidewall.