Toolstring and method for inner casing perforating, shattering annulus cement, and washing the first annulus in a second casing

A method of annulus cleaning an annulus-cemented casing portion of a first casing in a second casing in a petroleum well, comprising the steps of:

• running a drill pipe string-conveyed perforating gun into said well, wherein the perforation gun is run with a cement shattering device and a washing tool into said well;
• positioning said perforating gun at said cemented casing portion and activating first, shallow-perforating charges to make first, shallow perforations through said casing portion into a cement-filled annulus portion and leaving said second casing intact;
• activating said cement shattering device to provide combustion energy through said shallow perforations to disintegrate all or part of said cement within said first perforated annulus portion;
• and
• running the washing tool along said perforated casing portion, washing out all or part of said shattered cement from said perforated annulus portion.

A casing annulus cleaning tool string comprising:

• a drill pipe string with:
• a conveyed perforation gun;
• and
• a cement shattering device,
• wherein both the perforation gun and the cement shattering device are arranged near said drill pipe string's lower end, for being lowered into a casing with an annulus cemented casing portion about said casing in a petroleum well,
• wherein said perforating gun is arranged with:
• first, shallow-perforating charges for shooting first, shallow perforations through said casing portion into a first annulus, said shallow-perforating charges arranged for leaving a surrounding second casing intact;
• wherein said shattering device is arranged for being activated after said shallow-perforating charges to provide combustion energy through said shallow perforations to disintegrate all or part of said cement within said first perforated annulus, and
• wherein a washing tool is arranged above said perforation gun and cement shattering device on said drill pipe string, said washing tool for washing out said shattered cement from said annulus.